Gas stream multi-pollutants control systems and methods

ABSTRACT

In some embodiments, the invention provides systems and methods for removing carbon dioxide and/or additional components of waste gas streams, comprising contacting the waste gas stream with an aqueous solution, removing carbon dioxide and/or additional components from the waste gas stream, and containing the carbon dioxide and/or additional components, in one form or another, in a composition. In some embodiments, the composition is a precipitation material comprising carbonates, bicarbonates, or carbonates and bicarbonates. In some embodiments, the composition further comprises carbonate and/or bicarbonate co-products resulting from co-processing SOx, NOx, particulate matter, and/or certain metals. Additional waste streams such as liquid, solid, or multiphasic waste streams may be processed as well.

CROSS-REFERENCE

This application claims the benefit of U.S. Provisional PatentApplication No. 61/156,809, filed 2 Mar. 2009, titled “Gas StreamMulti-Pollutants Control System and Method”; U.S. Provisional PatentApplication No. 61/161,369, filed 18 Mar. 2009, titled “NeutralizingIndustrial Wastes Utilizing CO2 and a Divalent Cation Solution”; U.S.Provisional Patent Application No. 61/305,473, filed 17 Feb. 2010,titled “Gas Stream Multi-Pollutants Control System and Method”; and U.S.Provisional Patent Application No. 61/309,812, filed 2 Mar. 2010, titled“Gas Stream Multi-Pollutants Control Systems and Methods,” each of whichis incorporated herein by reference in its entirety.

BACKGROUND

Industrial waste gas streams from coal-fired power plants, cementplants, ore processing operations, and the like are a major source ofatmospheric pollution. Of particular concern are components resultingfrom combustion of fossil fuels, which components include carbondioxide; carbon monoxide; nitrogen oxides (NOx); sulfur oxides (SOx);sulfides; halides such as hydrogen chloride and hydrogen fluoride;particulate matter such as fly ash; metals including, but not limitedto, arsenic, beryllium, boron, cadmium, chromium, cobalt, lead,manganese, mercury, molybdenum, selenium, strontium, thallium, andvanadium; organics such as hydrocarbons, dioxins, and polynucleararomatic hydrocarbons (PAH); and radioactive materials.

Conventionally, components in such industrial waste gas streams areremoved in a series of steps wherein each component is removed in aseparate step, often in a separate unit. For example, to removeparticulate matter such as fly ash, a dust collector such as anelectrostatic precipitator (ESP) or fabric filter is used. To scrubgases such as NOx, a selective catalytic reduction (SCR) system is used.To scrub a gas such as SOx, a flue gas desulfurization (FGD) system isused. And to scrub CO₂ from a waste gas stream, amine gas treating(e.g., gas sweetening using monoethanolamine (MEA), diethanolamine(DEA), or methyldiethanolamine (MDEA)) may be used. As such, theconventional multi-step, multi-unit approach to removing components fromindustrial waste gas streams requires multiple, sometimes costly,technologies and results in multiple product streams, each of whichrequires specialized handling.

Thus, conventional removal of components of industrial waste gas streamsand handling materials derived therefrom is complex and may beexpensive.

SUMMARY

In some embodiments, the invention provides a method of treating anindustrial waste gas, wherein the gas comprises carbon dioxide and atleast one other component selected from the group consisting of SOx;NOx; a metal; a non-carbon dioxide acid gas; an organic; and particulatematter, comprising contacting the gas with a liquid under conditionsadapted to cause at least some of the carbon dioxide and the othercomponent or components to exit the gas and enter the liquid, whereinthe method is carried out in a single processor. In some embodiments,the gas is not pre-treated prior to entering the processor to removesome or all of the carbon dioxide or any of the other components. Insome embodiments, the gas is pre-treated prior to entering the processorto remove particulate matter. In some embodiments, the gas comprises atleast two other components, and wherein the two other components exitthe gas and enter the liquid. In some embodiments, the two othercomponents are SOx and a metal. In some embodiments, the metal comprisesa heavy metal. In some embodiments, the metal is selected from the groupconsisting of antimony, arsenic, barium, beryllium, boron, cadmium,chromium, cobalt, copper, lead, manganese, mercury, molybdenum, nickel,radium, selenium, silver, strontium, thallium, vanadium, and zinc. Insome embodiments, the metal is mercury. In some embodiments, the twoother components are SOx and a non-carbon dioxide acid gas. In someembodiments, the two other components are a metal and a non-carbondioxide acid gas. In some embodiments, the two other components are SOxand particulate matter. In some embodiments, the gas is not pre-treatedprior to entering the processor to remove some or all of the carbondioxide or any of the other components. In some embodiments, the liquidcomprises an aqueous solution. In some embodiments, the aqueous solutioncomprises divalent cations. In some embodiments, the method furthercomprises processing the aqueous solution to produce a compositioncomprising carbonates, bicarbonates, or a combination thereof, and theother component or a derivative thereof, or the other components and/orderivatives thereof, wherein the carbonates, bicarbonates, or thecombination thereof, is at least partially derived from the carbondioxide. In some embodiments, the composition comprises a slurrycomprising a solid and a supernatant. In some embodiments, the solidcomprises carbonates, bicarbonates, or a combination thereof. In someembodiments, the solid further comprises the other component or aderivative thereof, or the other components and/or derivatives thereof.In some embodiments, the method further comprised separating the solidfrom the supernatant. In some embodiments, the solid, when subjected toa leaching process consisting essentially of preparing 2×1 L of anextraction fluid consisting essentially of an aqueous solution of aceticacid, wherein each 1 L of the extraction fluid consists essentially of5.7 mL acetic acid in deionized water; grinding the solid such thatparticles of ground solid are less than 1 cm in the narrowest dimensionif the particles are not already less than 1 cm in the narrowestdimension; placing 100 g of the ground solid into an extraction vesselwith 2 L of the extraction fluid to produce an extraction composition;rotating the extraction vessel in an end-over-end fashion for 18±2 hoursat room temperature; filtering the extraction composition throughborosilicate glass fiber with a pore size of 0.6 μm to 0.8 μm to producea leachate; and adjusting pH of the leachate with 1N nitric acid to a pHof pH 2 or less than pH 2, produces a leachate comprising less than 0.2mg/L of mercury. In some embodiments, the leaching process produces aleachate comprising less than 5.0 mg/L arsenic. In some embodiments, theleaching process produces a leachate comprising less than 100 mg/Lbarium. In some embodiments, the leaching process produces a leachatecomprising less then 1.0 mg/L cadmium. In some embodiments, the leachingprocess produces a leachate comprising less than 5.0 mg/L chromium. Insome embodiments, the leaching process produces a leachate comprisingless than 5.0 mg/L lead. In some embodiments, the leaching processproduces a leachate comprising less than 1.0 mg/L selenium. In someembodiments, the leaching process produces a leachate comprising lessthan 5.0 mg/L silver. In some embodiments, the solid, when subjected toa carbon dioxide release protocol consisting essentially of grinding thesolid such that particles of ground solid are less than 1 cm in thenarrowest dimension if the particles are not already less than 1 cm inthe narrowest dimension and immersing the solid in a solution having apH between pH 4.8 and pH 5.2 and a temperature between 60 and 80° C. for48 hours, produces no more than 5 grams carbon dioxide per 100 gramssolid. In some embodiments, the solid, when subjected to a carbondioxide release protocol consisting essentially of grinding the solidsuch that particles of ground solid are less than 1 cm in the narrowestdimension if the particles are not already less than 1 cm in thenarrowest dimension and immersing the solid in a solution having a pHbetween pH 4.8 and pH 5.2 and a temperature between 60 and 80° C. for 48hours, produces no more than 5 grams carbon dioxide per 100 grams solid.In some embodiments, the contacting is carried out under conditionsadapted to cause at least 50% of the carbon dioxide and at least 50% ofthe other component or components to exit the gas and enter the liquid.

In some embodiments, the invention provides a method comprising (i)contacting a gas stream with an aqueous solution, wherein the gas streamcomprises carbon dioxide and at least one other component selected fromthe group consisting of SOx; NOx; a metal; a non-carbon dioxide acidgas; an organic; and particulate matter, under conditions adapted tocause at least some of the carbon dioxide and the other component orcomponents to exit the gas stream and enter the aqueous solution; and(ii) processing the aqueous solution to produce a composition comprisingcarbonates, bicarbonates, or a combination of carbonates andbicarbonates, and the other component or a derivative thereof, or theother components and/or derivatives thereof, wherein the carbonates,bicarbonates, or the combination of carbonates and bicarbonates, is atleast partially derived from the carbon dioxide. In some embodiments,the other component is selected from the group consisting of SOx, ametal, a non-carbon dioxide acid gas, and an organic. In someembodiments, the other component is selected from the group consistingof SOx and a metal. In some embodiments, the gas stream comprises atleast two other components and the processing produces a compositioncomprising carbonates, bicarbonates, or a combination of carbonates andbicarbonates, and the two other components and/or derivatives thereof.In some embodiments, the two other components are SOx and a metal. Insome embodiments, the metal comprises a heavy metal. In someembodiments, the metal is selected from the group consisting ofantimony, arsenic, barium, beryllium, boron, cadmium, chromium, cobalt,copper, lead, manganese, mercury, molybdenum, nickel, radium, selenium,silver, strontium, thallium, vanadium, and zinc. In some embodiments,the metal comprises mercury or mercury derivative. In some embodiments,the gas stream comprises at least three other components and theprocessing produces a composition comprising carbonates, bicarbonates,or a combination of carbonates and bicarbonates, and the three othercomponents and/or derivatives thereof. In some embodiments, the threeother components are SOx, a metal, and a non-carbon dioxide acid gas. Insome embodiments, the metal comprises mercury or mercury derivative. Insome embodiments, the non-carbon dioxide acid gas is selected from thegroup consisting of hydrogen chloride, hydrogen fluoride, and SO₃. Insome embodiments, the three other components are SOx, a metal, and anorganic. In some embodiments, the metal comprises mercury or mercuryderivative. In some embodiments, the composition comprises a solution.In some embodiments, the composition comprises a slurry comprising asolution and a solid. In some embodiments, the method further comprisesseparating the solid from the solution. In some embodiments, the solid,when subjected to a leaching process consisting essentially of preparing2×1 L of an extraction fluid consisting essentially of an aqueoussolution of acetic acid, wherein each 1 L of the extraction fluidconsists essentially of 5.7 mL acetic acid in deionized water; grindingthe solid such that particles of ground solid are less than 1 cm in thenarrowest dimension if the particles are not already less than 1 cm inthe narrowest dimension; placing 100 g of the ground solid into anextraction vessel with 2 L of the extraction fluid to produce anextraction composition; rotating the extraction vessel in anend-over-end fashion for 18±2 hours at room temperature; filtering theextraction composition through borosilicate glass fiber with a pore sizeof 0.6 μm to 0.8 μm to produce a leachate; and adjusting pH of theleachate with 1N nitric acid to a pH of pH 2 or less than pH 2, producesa leachate comprising less than 0.2 mg/L of mercury. In someembodiments, the solid, when subjected to a carbon dioxide releaseprotocol consisting essentially of grinding the solid such thatparticles of ground solid are less than 1 cm in the narrowest dimensionif the particles are not already less than 1 cm in the narrowestdimension and immersing the solid in a solution having a pH between pH4.8 and pH 5.2 and a temperature between 60 and 80° C. for 48 hours,produces no more than 5 grams carbon dioxide per 100 grams solid. Insome embodiments, the gas stream comprises gas produced in an industrialprocess. In some embodiments, the gas stream is a waste gas stream. Insome embodiments, the waste gas stream is produced at a power plant, achemical processing plant, a mechanical processing plant, a refinery, acement plant, or a steel plant. In some embodiments, the gas stream isnot processed to remove carbon dioxide or the other component orcomponents prior to entering the aqueous solution. In some embodiments,the gas stream comprises a metal or metal derivative and wherein the gasstream is processed to convert the metal or metal derivative to a formthat is more easily taken up by the aqueous solution. In someembodiments, the non-carbon dioxide acid gas comprises a gas selectedfrom the group consisting of hydrogen chloride, hydrogen fluoride, andSO₃. In some embodiments, at least 50% of the carbon dioxide and atleast 50% of the other component exit the gas and enter the liquid. Insome embodiments, at least 50% of the carbon dioxide and at least 80% ofthe other component exit the gas and enter the liquid. In someembodiments, at least 70% of the carbon dioxide and at least 70% of theother component exit the gas and enter the liquid. In some embodiments,the contacting and processing are carried out sequentially. In someembodiments, the contacting and processing are carried outsimultaneously. In some embodiments, the contacting and processing arecarried out in the same unit.

In some embodiments, the invention provides a composition produced byany of the foregoing methods.

In some embodiments, the invention provides a composition comprisingcarbonates, bicarbonates, or a combination thereof, and asulfur-containing compound, wherein the carbonates, bicarbonates, orcombination thereof have a relative carbon isotope composition (δ¹³C)value less than −5.00‰, and wherein the composition, when subjected to aleaching process consisting essentially of preparing 2×1 L of anextraction fluid consisting essentially of an aqueous solution of aceticacid, wherein each 1 L of the extraction fluid consists essentially of5.7 mL acetic acid in deionized water; grinding the solid such thatparticles of ground solid are less than 1 cm in the narrowest dimensionif the particles are not already less than 1 cm in the narrowestdimension; placing 100 g of the ground solid into an extraction vesselwith 2 L of the extraction fluid to produce an extraction composition;rotating the extraction vessel in an end-over-end fashion for 18±2 hoursat room temperature; filtering the extraction composition throughborosilicate glass fiber with a pore size of 0.6 μm to 0.8 μm to producea leachate; and adjusting pH of the leachate with 1N nitric acid to a pHof pH 2 or less than pH 2, produces a leachate comprising less than 2.0mg/L of mercury. In some embodiments, the leachate comprises less than1.5 mg/L of mercury. In some embodiments, the leachate comprises lessthan 1.0 mg/L of mercury. In some embodiments, the leachate comprisesless than 0.5 mg/L of mercury. In some embodiments, the leachatecomprises less than 0.2 mg/L of mercury. In some embodiments, theleachate comprises less than 0.05 mg/L of mercury. In some embodiments,the composition comprises mercury, a mercury derivative, or acombination thereof. In some embodiments, the relative carbon isotopecomposition value is less than 10.00‰. In some embodiments, thecomposition relative carbon isotope composition (δ¹³C) value less than−15.00‰. In some embodiments, the composition relative carbon isotopecomposition (δ¹³C) value less than −20.00‰. In some embodiments, thecomposition comprises at least 90% carbonates. In some embodiments, thecomposition comprises a calcium:magnesium ratio of 5:1. In someembodiments, the solid, when subjected to a carbon dioxide releaseprotocol consisting essentially of grinding the solid such thatparticles of ground solid are less than 1 cm in the narrowest dimensionif the particles are not already less than 1 cm in the narrowestdimension and immersing the solid in a solution having a pH between pH4.8 and pH 5.2 and a temperature between 60 and 80° C. for 48 hours,produces no more than 5 grams carbon dioxide per 100 grams solid.

In some embodiments, the invention provides a composition comprisingcarbonates, bicarbonates, or a combination thereof, and mercury, amercury derivative, or a combination thereof, wherein the carbonates,bicarbonates, or the combination thereof have a relative carbon isotopecomposition (δ¹³C) value less than −5.00‰, and wherein the composition,when subjected a leaching process consisting essentially of preparing2×1 L of an extraction fluid consisting essentially of an aqueoussolution of acetic acid, wherein each 1 L of the extraction fluidconsists essentially of 5.7 mL acetic acid in deionized water; grindingthe solid such that particles of ground solid are less than 1 cm in thenarrowest dimension if the particles are not already less than 1 cm inthe narrowest dimension; placing 100 g of the ground solid into anextraction vessel with 2 L of the extraction fluid to produce anextraction composition; rotating the extraction vessel in anend-over-end fashion for 18±2 hours at room temperature; filtering theextraction composition through borosilicate glass fiber with a pore sizeof 0.6 μm to 0.8 μm to produce a leachate; and adjusting pH of theleachate with 1N nitric acid to a pH of pH 2 or less than pH 2, producesa leachate comprising less than 2.0 mg/L of mercury. In someembodiments, the leachate comprises less than 1.5 mg/L of mercury. Insome embodiments, the leachate comprises less than 1.0 mg/L of mercury.In some embodiments, the leachate comprises less than 0.5 mg/L ofmercury. In some embodiments, the leachate comprises less than 0.2 mg/Lof mercury. In some embodiments, the leachate comprises less than 0.05mg/L of mercury. In some embodiments, the composition, when subjected toa carbon dioxide release protocol consisting essentially of grinding thecomposition such that particles of ground composition are less than 1 cmin the narrowest dimension if the particles are not already less than 1cm in the narrowest dimension and immersing the ground composition in asolution having a pH between pH 4.8 and pH 5.2 and a temperature between60 and 80° C. for 48 hours, produces no more than 5 grams carbon dioxideper 100 grams composition.

In some embodiments, the invention provides a composition comprisingcarbonates, bicarbonates, or a combination thereof, mercury, a mercuryderivative, or a combination thereof, and sulfur-containing compound,wherein the composition, (i) when subjected to a leaching processconsisting essentially of preparing 2×1 L of an extraction fluidconsisting essentially of an aqueous solution of acetic acid, whereineach 1 L of the extraction fluid consists essentially of 5.7 mL aceticacid in deionized water; grinding the solid such that particles ofground solid are less than 1 cm in the narrowest dimension if theparticles are not already less than 1 cm in the narrowest dimension;placing 100 g of the ground solid into an extraction vessel with 2 L ofthe extraction fluid to produce an extraction composition; rotating theextraction vessel in an end-over-end fashion for 18±2 hours at roomtemperature; filtering the extraction composition through borosilicateglass fiber with a pore size of 0.6 μm to 0.8 μm to produce a leachate;and adjusting pH of the leachate with 1N nitric acid to a pH of pH 2 orless than pH 2, produces a leachate comprising less than 0.2 mg/L ofmercury; and (ii) when subjected to a carbon dioxide release protocolconsisting essentially of grinding the composition such that particlesof ground composition are less than 1 cm in the narrowest dimension ifthe particles are not already less than 1 cm in the narrowest dimensionand immersing the ground composition in a solution having a pH betweenpH 4.8 and pH 5.2 and a temperature between 60 and 80° C. for 48 hours,produces no more than 5 grams carbon dioxide per 100 grams composition.

In some embodiments, the invention provides a system comprising (i) asource of an industrial waste gas operably connected to (ii) a processorconfigured to (a) process the gas to at least partially remove carbondioxide from the gas and also to at least partially remove at least oneother component from the gas, wherein the other component is selectedfrom the group consisting of SOx, NOx, a metal, particulate matter, anon-carbon dioxide acid gas, and an organic and (b) produce acomposition comprising a product comprising at least a portion of thecarbon dioxide, or one or more derivatives thereof, in combination withat least a portion of the other component or one or more derivativesthereof, wherein the composition is suitable for placement in theenvironment. In some embodiments, the composition comprises carbonates,bicarbonates, or a combination thereof. In some embodiments, the othercomponent is SOx or a metal selected from the group consisting ofantimony, arsenic, barium, beryllium, boron, cadmium, chromium, cobalt,copper, lead, manganese, mercury, molybdenum, nickel, radium, selenium,silver, strontium, thallium, thorium, uranium vanadium, and zinc;particulate matter; or a combination thereof. In some embodiments, thecomposition is suitable for placement in the environment in compliancewith Toxicity Characteristic Leaching Procedure, Extraction ProcedureToxicity Test, Synthetic Precipitation Leaching Procedure, CaliforniaWaste Extraction Test, Soluble Threshold Limit Concentration, AmericanSociety for Testing and Materials Extraction Test, Multiple ExtractionProcedure, or a combination thereof. In some embodiments, thecomposition is suitable for placement in the environment in compliancewith Toxicity Characteristic Leaching Procedure. In some embodiments,the system further comprises a composition conveyor for disposal of atleast a portion of the composition. In some embodiments, the compositionconveyor is configured to dispose of at least a portion of thecomposition underground. In some embodiments, the processor comprises agas-liquid contactor, a gas-liquid-solid contactor, a reactor, asettling tank, or a combination thereof. In some embodiments, theprocessor is further configured to produce a processed waste gas stream.In some embodiments, the processed waste gas stream is suitable forplacement in the environment in compliance with Reasonably AvailableControl Technology; Best Available Control Technology; MaximumAchievable Control Technology; Lowest Achievable Emission Rate, or acombination thereof. In some embodiments, the system further comprises atreatment system. In some embodiments, the treatment system comprises aliquid-solid separator for concentrating at least a portion of thecomposition and producing a concentrated composition and a supernatant.In some embodiments, the supernatant is suitable for placement in theenvironment. In some embodiments, the treatment system is configured torecirculate at least a portion of the supernatant back to the processor.In some embodiments, the concentrated composition is suitable forplacement in the environment in compliance with Toxicity CharacteristicLeaching Procedure, Extraction Procedure Toxicity Test, SyntheticPrecipitation Leaching Procedure, California Waste Extraction Test,Soluble Threshold Limit Concentration, American Society for Testing andMaterials Extraction Test, Multiple Extraction Procedure, or acombination thereof. In some embodiments, the system further comprises amanufacturing system for manufacturing a building material from at leasta portion of the concentrated composition. In some embodiments, themanufacturing system is configured for manufacturing cement,supplementary cementitious material, fine aggregate, mortar, coarseaggregate, concrete, pozzolan, or a combination thereof from theconcentrated composition. In some embodiments, the system furthercomprises a concentrated composition conveyor for disposal of at least aportion of the concentrated composition. In some embodiments, theconcentrated composition conveyor is configured to dispose of theconcentrated composition underground. In some embodiments, the systemfurther comprises an electrochemical system for producing hydroxide forprocessing the gas in the processor. In some embodiments, theelectrochemical system comprises an anode and a cathode. In someembodiments, the hydroxide is produced at the cathode. In someembodiments, chlorine is not formed at the anode. In some embodiments,oxygen is not formed at the anode. In some embodiments, the processor isoperably connected to an industrial plant comprising a power plant, achemical processing plant, a mechanical processing plant, a refinery, acement plant, or a steel plant. In some embodiments, a gas conveyoroperably connects the processor to the industrial plant. In someembodiments, the system is configured to be powered down during a periodof high demand on the industrial plant. In some embodiments, the system,the industrial plant, or a combination of the system and the industrialplant remain in compliance with Reasonably Available Control Technology;Best Available Control Technology; Maximum Achievable ControlTechnology; Lowest Achievable Emission Rate, or a combination thereof.

In some embodiments, the invention provides a system comprising (i) asource of an industrial waste gas comprising carbon dioxide and one ormore other components selected from the group consisting of SOx, NOx, ametal, non-carbon dioxide acid gas, an organic, and particulate matter;(ii) a processor configured to remove at least a portion of the carbondioxide and the other component or components from the gas in a singleprocessing unit; and (iii) a conduit operably connecting the source ofindustrial waste gas and the processor, wherein the conduit isconfigured to direct at least a portion of the industrial waste gas tothe processor. In some embodiments, the system does not comprise apre-processor between the source of the industrial waste gas and theprocessor wherein the pre-processor is configured to remove one or moreof the other components of the gas before the gas is passed to theprocessor. In some embodiments, the gas comprises at least two of theother components and wherein the processor is configured to remove atleast a portion of the carbon dioxide and the other components from thegas in a single processing unit.

In some embodiments the invention provides, a method comprising a)processing an industrial waste gas stream with an aqueous solution; b)removing carbon dioxide from the industrial waste gas stream and atleast one other component selected from the group consisting of SOx;NOx; carbon monoxide; a metal; particulate matter; a halide; and anorganic; and c) producing a carbonate- and/or bicarbonate-containingcomposition comprising the at least one other component or a productthereof, wherein the composition sequesters carbon dioxide and the atleast one other component, and wherein the composition is suitable forplacement in the environment. In some embodiments, the compositionsequesters carbon dioxide and at least two other components. In someembodiments, the composition sequesters carbon dioxide and at leastthree other components. In some embodiments, at least 50% of the carbondioxide is removed from the industrial waste stream. In someembodiments, at least 75% of at least one other component is removedfrom the industrial waste stream. In some embodiments, the metalcomprises antimony, arsenic, barium, beryllium, boron, cadmium,chromium, cobalt, copper, lead, manganese, mercury, molybdenum, nickel,radium, selenium, silver, strontium, thallium, thorium, uraniumvanadium, zinc, or a combination thereof. In some embodiments,particulate matter comprises fly ash, dust from calcining, or acombination thereof. In some embodiments, the halide comprises hydrogenchloride, hydrogen fluoride, or a combination thereof. In someembodiments, processing the industrial waste gas stream produces aprocessed waste gas stream that is suitable for placement in theenvironment in compliance with Reasonably Available Control Technology;Best Available Control Technology; Lowest Achievable Emission Rate, or acombination thereof. In some embodiments, the method further comprisesdisposing at least a portion of the composition above ground,underground, or underwater. In some embodiments, the method furthercomprises removing water from the composition to produce a supernatantand a concentrated composition. In some embodiments, the supernatant issuitable for placement in the environment. In some embodiments, themethod further comprises re-circulating the supernatant to the aqueoussolution. In some embodiments, the concentrated composition isconcentrated with respect to carbonates, bicarbonates, the at least oneother component, products of the at least one other component, or acombination thereof. In some embodiments, the concentrated compositioncomprises precipitation material. In some embodiments, the concentratedcomposition comprises greater than 25% precipitation material. In someembodiments, the concentrated composition comprises greater than 50%precipitation material. In some embodiments, the concentratedcomposition comprises greater than 75% precipitation material. In someembodiments, the precipitation material comprise salts of divalentcations. In some embodiments, the divalent cations comprise calcium,magnesium, or a combination thereof. In some embodiments, the divalentcations further comprise strontium. In some embodiments, theconcentrated composition is suitable for placement in the environment incompliance with Toxicity Characteristic Leaching Procedure, ExtractionProcedure Toxicity Test, Synthetic Precipitation Leaching Procedure,California Waste Extraction Test, Soluble Threshold Limit Concentration,American Society for Testing and Materials Extraction Test, MultipleExtraction Procedure, or a combination thereof. In some embodiments, themethod further comprises disposing at least a portion of theconcentrated composition above ground, underground, or underwater. Insome embodiments, the method further comprises using the concentratedcomposition in cement, fine aggregate, mortar, coarse aggregate,concrete, pozzolan, or a combination thereof. In some embodiments, themethod further comprises pre-treating the industrial waste gas stream toremove at least a portion of the particulate matter prior to processingthe industrial waste gas stream with the aqueous solution. In someembodiments, the method further comprises fortifying cement, fineaggregate, mortar, coarse aggregate, concrete, pozzolan with the removedparticulate matter. In some embodiments, the method further comprisespre-treating the industrial waste gas stream with an oxidant to oxidizeat least one component of the industrial waste gas stream prior toprocessing the industrial waste gas stream with the aqueous solution. Insome embodiments, the oxidant is hydrogen peroxide or chlorine. In someembodiments, the at least one component is NO, Hg, or a combinationthereof. In some embodiments, the method further comprises producing aproton-removing agent in an electrochemical system, wherein theproton-removing agent is added to the aqueous solution for processingthe industrial waste gas stream. In some embodiments, theproton-removing agent is hydroxide. In some embodiments, the hydroxideis formed at a cathode of the electrochemical system. In someembodiments, chlorine is not formed at an anode of the electrochemicalsystem. In some embodiments, oxygen is not formed at an anode of theelectrochemical system. In some embodiments, the method furthercomprises halting the processing of the industrial waste gas stream dueto high demand on an industrial plant providing the industrial waste gasstream. In some embodiments, the industrial waste gas stream remains incompliance with Reasonably Available Control Technology; Best AvailableControl Technology; Lowest Achievable Emission Rate, or a combinationthereof.

In some embodiments, the invention provides a composition produced byany of the above methods.

In some embodiments, the invention provides a composition comprisingcarbonates in combination with sulfates, wherein the carbonates have arelative carbon isotope composition (δ¹³C) value less than −5.00‰, andwherein the composition is suitable for placement in the environment incompliance with Toxicity Characteristic Leaching Procedure, ExtractionProcedure Toxicity Test, Synthetic Precipitation Leaching Procedure,California Waste Extraction Test, Soluble Threshold Limit Concentration,American Society for Testing and Materials Extraction Test, MultipleExtraction Procedure, or a combination thereof. In some embodiments, thecarbonates have a relative carbon isotope composition (δ¹³C) value lessthan −10.00‰. In some embodiments, the composition comprises 70-99.9%carbonates and 0.1-30% comprises sulfates. In some embodiments, thecomposition further comprises calcium, magnesium, or a combinationthereof. In some embodiments, the composition further comprisesbicarbonates, sulfites, nitrates, nitrites, silicates, aluminosilicates,chlorides, fluorides, oxides, particulate matter, or a combinationthereof. In some embodiments, the composition further comprisesantimony, arsenic, barium, beryllium, boron, cadmium, chromium, cobalt,copper, lead, manganese, mercury, molybdenum, nickel, radium, selenium,silver, strontium, thallium, thorium, uranium vanadium, zinc, or acombination thereof. In some embodiments, the composition comprises0.1-10,000 ppb mercury. In some embodiments, the composition comprisescement, fine aggregate, mortar, coarse aggregate, concrete, pozzolan, ora combination thereof.

In some embodiments, the invention provides a system comprising aprocessor configured for processing carbon dioxide from an industrialwaste gas stream and at least one other component from the waste gasstream selected from the group consisting of SOx, NOx, carbon monoxide,a metal, particulate matter, a halide, and an organic and producing acomposition comprising a product resulting from processing carbondioxide in combination with the at least one other component or aproduct thereof, wherein the composition is suitable for placement inthe environment. In some embodiments, the composition resulting fromprocessing carbon dioxide comprises carbonates, bicarbonates, orcarbonates and bicarbonates. In some embodiments, the at least one othercomponent is SOx; a metal selected from the group consisting ofantimony, arsenic, barium, beryllium, boron, cadmium, chromium, cobalt,copper, lead, manganese, mercury, molybdenum, nickel, radium, selenium,silver, strontium, thallium, thorium, uranium vanadium, and zinc;particulate matter; or a combination thereof. In some embodiments, thecomposition is suitable for placement in the environment in compliancewith Toxicity Characteristic Leaching Procedure, Extraction ProcedureToxicity Test, Synthetic Precipitation Leaching Procedure, CaliforniaWaste Extraction Test, Soluble Threshold Limit Concentration, AmericanSociety for Testing and Materials Extraction Test, Multiple ExtractionProcedure, or a combination thereof. In some embodiments, the systemfurther comprises a composition conveyor for disposal of at least aportion of the composition. In some embodiments, the compositionconveyor is configured to dispose of at least a portion of thecomposition underground. In some embodiments, the processor comprises agas-liquid contactor, a gas-liquid-solid contactor, a reactor, asettling tank, of a combination thereof. In some embodiments, theprocessor is further configured to produce a processed waste gas stream.In some embodiments, the processed waste gas stream is suitable forplacement in the environment in compliance with Reasonably AvailableControl Technology; Best Available Control Technology; Lowest AchievableEmission Rate, or a combination thereof. In some embodiments, the systemfurther comprises a treatment system. In some embodiments, the treatmentsystem comprises a liquid-solid separator for concentrating at least aportion of the composition and producing a concentrated composition anda supernatant. In some embodiments, the supernatant is suitable forplacement in the environment. In some embodiments, the treatment systemis configured to recirculate at least a portion of the supernatant backto the processor. In some embodiments, the concentrated composition issuitable for placement in the environment in compliance with ToxicityCharacteristic Leaching Procedure, Extraction Procedure Toxicity Test,Synthetic Precipitation Leaching Procedure, California Waste ExtractionTest, Soluble Threshold Limit Concentration, American Society forTesting and Materials Extraction Test, Multiple Extraction Procedure, ora combination thereof. In some embodiments, the system further comprisesa manufacturing system for manufacturing a building material from atleast a portion of the concentrated composition. In some embodiments,the manufacturing system is configured for manufacturing cement, fineaggregate, mortar, coarse aggregate, concrete, pozzolan, or acombination thereof from the concentrated composition. In someembodiments, the system further comprises a concentrated compositionconveyor for disposal of at least a portion of the concentratedcomposition. In some embodiments, the concentrated composition conveyoris configured to dispose of the concentrated composition underground. Insome embodiments, the system further comprises an electrochemical systemfor producing hydroxide for processing the industrial waste gas streamin the processor. In some embodiments, the electrochemical systemcomprises an anode and a cathode. In some embodiments, the hydroxide isproduced at the cathode. In some embodiments, chlorine is not formed atthe anode. In some embodiments, oxygen is not formed at the anode. Insome embodiments, the processor is operably connected to an industrialplant comprising a power plant, a chemical processing plant, amechanical processing plant, a refinery, a cement plant, a steel plant,or any other industrial plant that produces CO₂ as a by-product of fuelcombustion or some other processing step. In some embodiments, a gasconveyor operably connects the processor to the industrial plant. Insome embodiments, the system is configured to be powered down during aperiod of high demand on the industrial plant. In some embodiments, thesystem, the industrial plant, or a combination of the system and theindustrial plant remain in compliance with Reasonably Available ControlTechnology; Best Available Control Technology; Lowest AchievableEmission Rate, or a combination thereof.

In some embodiments, the invention provides a method comprisingcontacting a waste gas stream with a metal ion-containing aqueoussolution, whereby at least three of the following components are removedfrom the waste gas stream and contained in an insoluble stableprecipitation material: carbon dioxide; carbon monoxide; nitrogen oxides(NOx); sulfur oxides (SOx); hydrogen sulfide; hydrogen chloride;hydrogen fluoride; fly ash; dusts; metals including arsenic, beryllium,boron, cadmium, chromium, chromium VI, cobalt, lead, manganese, mercury,molybdenum, selenium, strontium, thallium; hydrocarbons; radioactivematerials; dioxins; and PHA. In some embodiments, the invention providesa method comprising contacting an industrial waste gas stream with anaqueous solution comprising divalent cations; removing carbon dioxideand at least two components selected from the group consisting of carbonmonoxide; nitrogen oxides (NOx); sulfur oxides (SOx); hydrogen sulfide;hydrogen chloride; hydrogen fluoride; fly ash; dusts; metals includingarsenic, beryllium, boron, cadmium, chromium, chromium VI, cobalt, lead,manganese, mercury, molybdenum, selenium, strontium, thallium;hydrocarbons; radioactive materials, dioxins, and PAH; and producing acarbonate- and/or bicarbonate-containing composition of the divalentcations comprising the at least two components or products of the atleast two components, wherein the carbonate- and/orbicarbonate-containing composition serves to sequester carbon dioxide.In some embodiments, at least 1%, 5%, 10%, 25%, 30%, 40%, 50%, 60%, 70%,75%, 80%, 85%, 90%, or 95% of one or more of the components are removed,wherein each of the one or more components may be removed at the same ora different percentage level. In some embodiments, substantially all ofeach one or more of the component are removed. In some embodiments, theaqueous solution comprises calcium or magnesium ions. In someembodiments, the aqueous solution is selected from seawater, brines,inland water and a solution comprising dissolved mafic minerals. In someembodiments, the precipitation material comprises carbonates,bicarbonates, nitrates and/or sulfates or sulfites. In some embodiments,the precipitation material comprises mercury, selenium, and fly ash. Insome embodiments, the precipitation material comprises metal complexes,dust, and particulate matter. In some embodiments, the method furthercomprises pre-treating the waste gas stream to remove particulate mattertherein before contact with the aqueous solution. In some embodiments,the method further comprises pre-treating the waste gas stream tooxidize components therein before contact with the aqueous solution. Insome embodiments, the method further comprises converting nitrous oxideto nitrogen dioxide; sulfur trioxide to sulfur dioxide; carbon monoxide,hydrocarbons, radioactive materials, dioxins, and/or PAH to carbondioxide; and/or metals to metal oxides before contacting the waste gasstream with the aqueous solution. In some embodiments, the methodfurther comprises extracting a supernatant liquid and a desalinatedwater from the aqueous solution. In some embodiments, the method furthercomprises re-circulating the supernatant liquid to the aqueous solution.In some embodiments, the precipitation material comprises a hydrauliccement. In some embodiments, the precipitation material comprises anaggregate. In some embodiments, the pH of the metal ion-containingsolution is 10, 11, 12, or higher. In some embodiments, the metalion-containing solution is adjusted to a substantially constant pH valueusing hydroxide ions from an electrochemical process that does notgenerate a gas at the anode.

In some embodiments, the invention provides a method comprisingcontacting a waste gas stream comprising carbon dioxide, nitrogenoxides, and sulfur oxides with a metal ion-containing aqueous solutionand causing precipitation of a precipitation material that comprisescarbon dioxide, sulfur oxide and mercury from the waste gas stream. Insome embodiments, the invention provides a method comprising contactingan industrial waste gas stream comprising carbon dioxide, NOx, and SOxwith an aqueous solution comprising divalent cations and producing acarbonate- and/or bicarbonate-containing composition of the divalentcations comprising products of NOx, SOx, or a combination thereof,wherein the carbonate- and/or bicarbonate-containing composition servesto sequester carbon dioxide. In some embodiments, the method furthercomprises processing the waste gas stream before or after said contactto remove one or more of particulate matter and nitrogen oxides. In someembodiments, the processing occurs in one or more steps. In someembodiments, the method further comprises pre-treating the waste gasstream to remove particulate matter before contacting the waste gasstream with the aqueous solution. In some embodiments, the methodfurther comprises pre-treating the waste gas stream to convert nitrousoxide to nitrogen dioxide; sulfur trioxide to sulfur dioxide; carbonmonoxide, hydrocarbons, dioxins, and/or PAH to carbon dioxide; and ormetals to metal oxides before contacting the waste gas stream with theaqueous solution. In some embodiments, the aqueous solution comprisescalcium or magnesium ions. In some embodiments, the metal ion-containingsolution is selected from seawater, brines, inland water and an aqueoussolution comprising dissolved mafic minerals. In some embodiments, themethod further comprises extracting a supernatant liquid and adesalinated water from the aqueous solution. In some embodiments, themethod further comprises re-circulating at least a portion of thesupernatant liquid to the aqueous solution. In some embodiments, themethod further comprises removing substantially all carbon dioxide,mercury and/or sulfur oxides from the waste gas stream. In someembodiments, the method further comprises removing 5%, 10%, 20%, 30%,40%, 50%, 60%, 70%, 80% or more of carbon dioxide, mercury and/or sulfuroxides from the waste gas stream. In some embodiments, the precipitationmaterial comprises calcium carbonate, magnesium carbonate, calciummagnesium carbonate, and metal complexes. In some embodiments, theprecipitation material comprises one or more of the following: fly ash;dusts; metals including arsenic, beryllium, boron, cadmium, chromium,chromium VI, cobalt, lead, manganese, mercury, molybdenum, selenium,strontium, and thallium.

In some embodiments, the invention provides a method comprisingcontacting a flue gas from an industrial source with a metalion-containing aqueous solution under conditions that cause theprecipitation of carbon dioxide and at least two other component of theflue gas into an insoluble stable precipitation material. In someembodiments, the invention provides a method comprising contacting aflue gas from an industrial source with an aqueous solution comprisingdivalent cations under conditions that produce a carbonate- and/orbicarbonate-containing composition of the divalent cations comprisingthe products of at least two components of the flue gas, wherein thecarbonate- and/or bicarbonate-containing composition serves to sequestercarbon dioxide. In some embodiments, the method further comprisestreating the flue gas to enhance the inclusion of the at least one ofthe two other components of the flue gas or a derivative therefrom intothe insoluble stable precipitation material.

In some embodiments, the invention provides a method of treating a fluegas from an industrial source to remove undesirable components of theflue gas comprising treating the flue gas to remove particulate matterthen treating the flue gas to remove carbon dioxide, mercury, and sulfuroxides therefrom. In some embodiments, the flue gas is further processedbefore or after said treatment to remove one or more of particulatematter and nitrogen oxides. In some embodiments, the flue gas is furtherprocessed in one or more steps.

In some embodiments, the invention provides a process for treating awaste gas stream comprising carbon dioxide and sulfur oxides, comprisingremoving at least 50% of the carbon dioxide and at least 50% of thesulfur oxides from the waste gas stream by precipitating in a singlestep the carbon dioxide, sulfur oxides in an insoluble composition. Insome embodiments, the invention provides a process for treating anindustrial waste gas stream comprising carbon dioxide and SOx,comprising: removing at least 50% of the carbon dioxide and at least 50%of the SOx from the waste gas stream by producing a compositioncomprising carbonates, bicarbonates, sulfites, sulfates, or acombination thereof. In some embodiments, the waste gas stream furthercomprises mercury. In some embodiments, the method further comprisesremoving at least 50% of the mercury from the waste gas stream. In someembodiments, the waste gas stream further comprises nitrogen oxides andwherein the process further comprises removing at least 50% of thenitrogen oxide in the single process. In some embodiments, the carbondioxide and sulfur oxides are precipitated from an aqueous solutioncomprising divalent cations. In some embodiments, the divalent cationscomprise calcium and magnesium. In some embodiments, the method furthercomprises pre-treating the waste gas stream to render one or more of itsconstituents more amenable to precipitation.

In some embodiments, the invention provides a process for treating awaste gas stream, wherein the waste gas stream comprises carbon dioxideand mercury, and wherein the process comprises removing at least 50% ofthe carbon dioxide and at least 50% of the mercury in a single processthat comprises precipitating the carbon dioxide and mercury. In someembodiments, the invention provides a process for treating an industrialwaste gas stream comprising carbon dioxide and mercury, comprising:removing at least 50% of the carbon dioxide and at least 50% of themercury by producing a composition comprising carbonates, bicarbonates,mercury, mercury compounds, or a combination thereof.

In some embodiments, the invention provides a method of treating a fluegas from an industrial source to remove undesirable components of theflue gas, comprising treating the flue gas to remove particulate matterthen treating the flue gas to remove both carbon dioxide and sulfuroxides (SOx). In some embodiments, the invention provides a method oftreating a flue gas from an industrial source to remove undesirablecomponents of the flue gas comprising treating the flue gas to removeparticulate matter then treating the flue gas to remove carbon dioxide,SOx, and mercury therefrom.

In some embodiments, the invention provides a system comprising aprocessor adaptable for contacting a waste gas stream with a metalion-containing aqueous solution, wherein at least three of the followingcomponents are removable from the waste gas stream and can be containedin an insoluble stable precipitation material: carbon dioxide; carbonmonoxide; nitrogen oxides sulfur oxides; hydrogen sulfide; hydrogenchloride; hydrogen fluoride; fly ash; dusts; metals including arsenic,beryllium, boron, cadmium, chromium, chromium VI, cobalt, lead,manganese, mercury, molybdenum, selenium, strontium, thallium;hydrocarbons; radioactive material; dioxins; and PAH. In someembodiments, the invention provides a system comprising a processorconfigured for contacting an industrial waste gas stream with an aqueoussolution comprising divalent cations; removing carbon dioxide and atleast two components selected from the group consisting of carbonmonoxide; nitrogen oxides sulfur oxides; hydrogen sulfide; hydrogenchloride; hydrogen fluoride; fly ash; dusts; metals including arsenic,beryllium, boron, cadmium, chromium, chromium VI, cobalt, lead,manganese, mercury, molybdenum, selenium, strontium, thallium;hydrocarbons; radioactive material, dioxins, and PAH; and producing acarbonate- and/or bicarbonate-containing composition of the divalentcations comprising the at least two components or products of the atleast two components, wherein the carbonate- and/orbicarbonate-containing composition serves to sequester carbon dioxide.In some embodiments, the system further comprises a hydroxide ionssystem for supplying hydroxide ions to the processor. In someembodiments, the system further comprises an aqueous solution system forsupplying a divalent cation-containing solution to the processor. Insome embodiments, the waste gas stream comprises carbon dioxide,nitrogen oxides, and sulfur oxides. In some embodiments, the waste gasstream comprises particulate matter, fly ash, arsenic, beryllium, boron,cadmium, chromium, chromium VI, cobalt, lead, manganese, mercury,molybdenum, selenium, strontium, thallium, vanadium, dust, radio activematerials, dioxins, and PAH compounds. In some embodiments, theprocessor is adapted for receiving combustion gases and particulatematter from a coal-fired power plant, a cement plant, a foundry, asmelter, a refinery or an ore processing operation in the waste gasstream. In some embodiments, the aqueous solution system is adapted forsupplying calcium and magnesium ions to the processor. In someembodiments, the aqueous system is adapted for supplying a divalentcation-containing water to the processor, comprising seawater, brines,inland water and an aqueous solution formed by dissolving maficminerals. In some embodiments, the aqueous system is adapted forsupplying a divalent cation-containing solution to the processor fromdissolved mafic minerals selected from olivine, pyroxene, amphibole,biotite, basalt and gabbro. In some embodiments, the processor isadapted for causing removal of carbon dioxide, nitrogen oxide, sulfuroxides and mercury from the waste gas stream into the aqueous solution.In some embodiments, the processor is adapted for removing nitrogenoxides, sulfur oxides and carbon dioxide from the waste gas stream. Insome embodiments, the processor is adapted for removing carbon dioxide,nitrogen oxides, sulfur oxides or particulate matter, and combinationsthereof from the waste gas stream into the aqueous solution. In someembodiments, the system further comprises a system capable of extractinga supernatant liquid and desalinated water from the precipitation in theaqueous solution. In some embodiments, the system further comprises asystem capable of re-circulating at least a portion of the supernatantliquid to the aqueous solution. In some embodiments, the system furthercomprises a liquid-solid separator for separating a precipitationmaterial and a supernatant solution from the aqueous solution. In someembodiments, the system further comprises a dryer for producing a driedproduct from the precipitation material.

In some embodiments, the invention provides a synthetic compositioncomprising calcium carbonate, magnesium carbonate, and calcium sulfateand/or calcium sulfite, wherein the carbonate and the sulfate and/orsulfite are of fossil fuel origin in a combustion waste gas stream. Insome embodiments, the invention provides a synthetic compositioncomprising salts of Ca²⁺, Mg²⁺, or Ca²⁺ and Mg²⁺, wherein thecounterions comprise carbonates in combination with sulfates and/orsulfites, and wherein the carbonates have a relative carbon isotopecomposition (δ¹³C) value less than −5.00‰.

In some embodiments, the invention provides a synthetic compositioncomprising two or more of: calcium or magnesium carbonate, calciumsulfate or sulfite, mercury, calcium nitrate, particulate matter, lead,arsenic precipitated from a combustion gas stream. In some embodiments,the invention provides a synthetic composition comprising salts of Ca²⁺,Mg²⁺, or Ca²⁺ and Mg²⁺, wherein the counterions comprise carbonates incombination with sulfates, sulfites, nitrates, nitrites, mercury,mercury compounds, lead, arsenic, particulate matter, or a combinationthereof, and wherein the carbonates have a relative carbon isotopecomposition (δ¹³C) value less than −5.00‰.

In some embodiments, the invention provides a synthetic compositioncomprising three or more of: calcium or magnesium carbonate, calciumsulfate or sulfite, mercury, calcium nitrate, particulate matter, lead,cadmium, arsenic precipitated form a combustion gas stream.

In some embodiments, the invention provides a synthetic compositioncomprising 70-99% calcium and magnesium carbonates, and 1-30% calciumand/or magnesium sulfates and sulfites precipitated from a combustiongas stream. In some embodiments, the composition further comprises0.00001-0.1% mercury compounds. In some embodiments, the compositionfurther comprises 1-25% nitrate or nitrite compounds. In someembodiments, the composition comprises a building material. In someembodiments, the composition comprises a cement, an aggregate, apozzolan, a mortar, or a combination thereof. In some embodiments, theinvention provides a synthetic composition comprising salts of Ca²⁺,Mg²⁺, or Ca²⁺ and Mg²⁺, wherein 70-99% of the synthetic compositioncomprises carbonates, and 1-30% comprises sulfates and/or sulfites andfurther wherein the carbonates have a relative carbon isotopecomposition (δ¹³C) value less than −5.00‰.

In some embodiments, the invention provides a method of neutralizing anindustrial waste, comprising contacting a first waste stream with asecond waste stream in the presence of an aqueous divalent cationsolution, whereby constituents in at least one of the waste streams areneutralized. In some embodiments, the first waste stream comprises abase, and the second waste stream comprises carbon dioxide. In someembodiments, the constituents in the first waste stream comprises sodiumhydroxide, magnesium hydroxide, calcium hydroxide, or calcium oxide. Insome embodiments, the first waste stream comprises red mud and/or flyash. In some embodiments, the aqueous divalent cation solution comprisesalkaline earth metal ions. In some embodiments, the aqueous divalentcation solution comprises calcium and/or magnesium ions. In someembodiments, the aqueous divalent cation solution comprises saltwater.In some embodiments, the aqueous divalent cation solution comprisesseawater, brackish water, brine, or an aqueous solution comprisingdissolved mafic minerals. In some embodiments, the method furthercomprises forming a precipitation material in the aqueous divalentcation solution. In some embodiments, the precipitation materialcomprises a divalent cation carbonate. In some embodiments, theprecipitation material comprises neutralized red mud and/or neutralizedfly ash. In some embodiments, the precipitation material comprisesbicarbonates, nitrates and/or sulfates and/or sulfites. In someembodiments, the precipitation material comprises mercury and/orselenium. In some embodiments, the precipitation material comprisesmetal complexes, dust, and particulate matter. In some embodiments, atleast 1%, 5%, 10%, 25%, 30%, 40%, 50%, 60%, 70%, 80%, or 90% ofconstituents in the first and second waste streams are neutralized. Insome embodiments, substantially all of constituents in the first andsecond waste streams are neutralized. In some embodiments, the methodfurther comprises pre-treating the second waste stream to removeparticulate matter therein before contact with the aqueous solution. Insome embodiments, the method further comprises pre-treating the secondwaste stream to oxidize components therein before contact with theaqueous solution. In some embodiments, the method further comprisesextracting a supernatant liquid and a desalinated water from thedivalent cation solution. In some embodiments, the method furthercomprises re-circulating at least a portion of the supernatant liquid tothe aqueous divalent cation solution. In some embodiments, theprecipitation material comprises a hydraulic cement. In someembodiments, the precipitation material comprises an aggregate. In someembodiments, the pH of the first waste stream is 10, 11, 12 or higher.In some embodiments, the pH of divalent cation solution is adjusted to asubstantially constant pH value by contact with the first waste stream.In some embodiments, the pH of divalent cation solution is adjusted to asubstantially constant pH value using hydroxide ions from anelectrochemical process that does not generate a gas at the anode.

In some embodiments, the invention provides a method of neutralizing anindustrial waste, comprising contacting the waste with a waste gasstream comprising carbon dioxide and a liquid stream comprising anaqueous divalent cation solution, whereby the pH of the waste isneutralized. In some embodiments, the waste comprises red mud and/or flyash. In some embodiments, the aqueous divalent cation solution comprisesalkaline earth metal ions. In some embodiments, the aqueous divalentcation solution comprises calcium and/or magnesium ions. In someembodiments, the aqueous divalent cation solution comprises saltwater.In some embodiments, the divalent cation-containing aqueous solutioncomprises seawater, brackish water, brine, or an aqueous solutioncomprising dissolved mafic minerals. In some embodiments, the waste gasstream comprises carbon dioxide formed by combusting fossil fuels. Insome embodiments, the method further comprises forming a precipitationmaterial in the aqueous divalent cation solution. In some embodiments,the precipitation material comprises a divalent cation carbonate.

In some embodiments, the precipitation material comprises calciumcarbonate, magnesium carbonate, calcium magnesium carbonate, and metalcomplexes. In some embodiments, the precipitation material comprises oneor more of the following: red mud, fly ash; dusts; metals includingarsenic, beryllium, boron, cadmium, chromium, chromium VI, cobalt, lead,manganese, mercury, molybdenum, selenium, strontium, and thallium. Insome embodiments, the method further comprises processing the waste gasstream before or after said contact to remove one or more of particulatematter and nitrogen oxides. In some embodiments, the method furthercomprises extracting a supernatant liquid and a desalinated water fromthe aqueous solution. In some embodiments, the method further comprisesre-circulating at least a portion of the supernatant liquid to theaqueous solution. In some embodiments, the method further comprisesremoving substantially all carbon dioxide, mercury, and/or sulfur oxidesfrom the waste gas stream. In some embodiments, the method furthercomprises removing 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% or more ofhydroxide ions from the waste.

In some embodiments, the invention provides a waste treatment systemcomprising a processor adaptable for contacting a gaseous source with awaste source and a cation ion-containing aqueous solution, wherein theprocessor is operable to neutralize constituents in the waste source bycontact with the aqueous solution. In some embodiments, the systemfurther comprises a base system for supplying hydroxide ions to theprocessor. In some embodiments, the system further comprises an aqueoussolution system for supplying a divalent cation-containing solution tothe processor. In some embodiments, the waste gas stream source providescarbon dioxide, nitrogen oxides, and sulfur oxides to the processor, andthe waste source is adaptable for supplying red mud and/or fly ash tothe processor. In some embodiments, the waste gas stream sourcecomprises particulate matter, fly ash, arsenic, beryllium, boron,cadmium, chromium, chromium VI, cobalt, lead, manganese, mercury,molybdenum, selenium, strontium, thallium, vanadium, dust, radio activematerials, dioxins, and PAH compounds. In some embodiments, theprocessor is capable of receiving combustion gases and particulatematter from a coal-fired power plant, a cement plant, a foundry, asmelter, a refinery or an ore processing operation in the waste gasstream. In some embodiments, the aqueous solution system is capable ofsupplying calcium and magnesium ions to the processor. In someembodiments, the aqueous system is capable of supplying a divalentcation-containing water to the processor, comprising seawater, brines,inland water and an aqueous solution formed by dissolving maficminerals. In some embodiments, the aqueous system is capable ofsupplying a divalent cation-containing solution to the processor fromdissolved mafic minerals selected from olivine, pyroxene, amphibole,biotite, basalt and gabbro. In some embodiments, the processor iscapable of causing removal of carbon dioxide, nitrogen oxide, sulfuroxides and mercury from the waste gas stream into the aqueous solution.In some embodiments, the system further comprises a liquid-solidseparator capable of extracting a supernatant liquid and desalinatedwater from the precipitation in the aqueous solution. In someembodiments, the system further comprises a re-circulating system forcirculating at least a portion of the supernatant liquid to the aqueoussolution. In some embodiments, the system further comprises a dryer forproducing a dried product from the precipitation material.

In some embodiments, the invention provides a synthetic compositioncomprising red mud and/or fly ash, calcium carbonate and/or magnesiumcarbonate, calcium sulfate and/or calcium sulfite, wherein thecarbonates and the sulfates and/or sulfites are of fossil fuel originand are provided in a combustion waste gas stream.

In some embodiments, the invention provides a synthetic compositioncomprising red mud and/or fly ash, 70-99% calcium and/or magnesiumcarbonates, and 1-30% calcium and/or magnesium sulfates and/or sulfitesprecipitated from a combustion gas stream. In some embodiments, thecomposition further comprises 0.00001-0.1% mercury compounds. In someembodiments, the composition further comprises 1-25% nitrate or nitritecompounds. In some embodiments, the composition comprises a buildingmaterial. In some embodiments, the composition comprises a cement, anaggregate, a pozzolan, a mortar, or a combination thereof.

In some embodiments, the invention provides a method of forming asynthetic hydraulic cement composition, comprising contacting a wastegas stream (e.g., combustion gas stream) with a divalentcation-containing aqueous solution to cause precipitation of the cementcomposition. In various embodiments, the cement composition comprisesparticles and precipitation material formed by reacting the componentsof the waste gas stream with alkaline earth metal ions in the aqueoussolution to from mineralized salts and metal complexes. In variousembodiments, the precipitation material is recovered and utilized as,for example, hydraulic cement and/or building materials as described incommonly assigned U.S. patent application Ser. No. 12/344,019, filed 24Dec. 2008, which is incorporated herein by reference in its entirety. Byutilizing the precipitation material as a hydraulic cement (e.g., inbuilding materials), the components of the waste gas stream that areremoved can be sequestered for an indefinite term. In variousembodiments, hydroxide ions are supplied to the aqueous solution tocause removal of particulate matter and reaction of components of thewaste gas stream with the aqueous solution to form the precipitationmaterial. In various embodiments, portions of a supernatant solutionobtained on removing the precipitation material from the aqueoussolution are re-circulated to the aqueous solution. In variousembodiments, the system and method are adaptable for batch, semi-batchor continuous flows, including re-circulating a portion of supernatantsolution formed by separating the precipitation material from thesaltwater.

Accordingly, constituents of various industrial waste streams (e.g.,waste gas streams, industrial waste sources of proton-removing agents ordivalent cations, etc.) may be neutralized for disposal and/or utilizedas building product (e.g., a hydraulic cement compositions). In variousembodiments, the system and method are adaptable for batch, semi-batchor continuous flows, including re-circulating a portion of supernatantsolution formed upon separating the precipitation material from thedivalent cation solution. Since removal of the components from variousindustrial waste streams, formation of compositions (e.g., precipitationmaterial), and, optionally, recovery of precipitation material are allachievable in one unit operation, the removal of various components(e.g., pollutants) from the various industrial waste streams may besimplified.

DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIG. 1A provides a system of the invention comprising a processor,wherein the processor is configured to process a variety of gasescomprising carbon dioxide.

FIG. 1B provides a system of the invention comprising a processor and atreatment system, wherein the treatment system is configured to treatcompositions from the processor.

FIG. 1C provides a system of the invention comprising a processor and anoptional treatment system, wherein the processor comprises a contactorand a reactor.

FIG. 1D provides a system of the invention comprising a processor and atreatment system, wherein supernatant from the treatment system mayoptionally be recirculated to the processor.

FIG. 1E provides a system of the invention comprising a processor, atreatment system, and an electrochemical system, wherein supernatantfrom the treatment system may optionally be recirculated to theprocessor, the electrochemical system, or a combination thereof.

FIG. 1F provides a system of the invention comprising a gas-liquid orgas-liquid-solid contactor, wherein the contactor is configured forrecirculation.

FIG. 2A provides a system of the invention, wherein the system isconfigured to produce a refined composition of the invention.

FIG. 2B provides a system of the invention, wherein the system isoptionally configured to treat gases comprising carbon dioxide prior toprocessing the gases.

FIG. 2C provides a system of the invention, wherein the system isconfigured to produce a building material of the invention.

FIG. 3 provides an electrochemical system of the invention.

FIG. 4 provides a method for contacting a gaseous stream with a divalentcation-containing aqueous solution.

FIG. 5 provides a method for contacting a gaseous stream comprisingcarbon dioxide, nitrogen oxides, and sulfur oxides with a divalentcation-containing aqueous solution.

FIG. 6 provides a method for contacting a flue gas from an industrialsource with a divalent cation-containing aqueous solution.

FIG. 7 provides a method for treating a flue gas to remove particulatesthen treating the flue gas to remove carbon dioxide, mercury, and sulfuroxides therefrom.

FIG. 8 provides a method for removing at least 50% of the carbon dioxideand at least 50% of the sulfur oxides from the gaseous stream.

FIG. 9 provides a method for treating a gas stream, wherein the gasstream comprises carbon dioxide and mercury, and wherein the methodcomprises removing at least 50% of the carbon dioxide and at least 50%of the mercury in a single process.

FIG. 10 provides a method for contacting a first waste stream with asecond waste stream in the presence of an aqueous divalent cationsolution, whereby constituents in at least one of the waste streams areneutralized.

FIG. 11 provides a method for contacting waste with a gaseous streamcomprising carbon dioxide and a liquid stream comprising an aqueousdivalent cation solution, whereby the pH of the waste is neutralized.

FIG. 12A and FIG. 12B provide a comparison of morphologies betweenlaboratory-synthesized magnesium carbonates with synthetic flue gas (15%CO₂, 3.5% O₂, balance N₂) without SO₂ (FIG. 12A) and with SO₂ (FIG.12B).

DESCRIPTION

Before the invention is described in greater detail, it is to beunderstood that the invention is not limited to particular embodimentsdescribed herein as such embodiments may vary. It is also to beunderstood that the terminology used herein is for the purpose ofdescribing particular embodiments only, and is not intended to belimiting, since the scope of the invention will be limited only by theappended claims. Unless defined otherwise, all technical and scientificterms used herein have the same meaning as commonly understood by one ofordinary skill in the art to which this invention belongs.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimit of that range and any other stated or intervening value in thatstated range, is encompassed within the invention. The upper and lowerlimits of these smaller ranges may independently be included in thesmaller ranges and are also encompassed within the invention, subject toany specifically excluded limit in the stated range. Where the statedrange includes one or both of the limits, ranges excluding either orboth of those included limits are also included in the invention.

Certain ranges are presented herein with numerical values being precededby the term “about” The term “about” is used herein to provide literalsupport for the exact number that it precedes, as well as a number thatis near to or approximately the number that the term precedes. Indetermining whether a number is near to or approximately a specificallyrecited number, the near or approximating unrecited number may be anumber, which, in the context in which it is presented, provides thesubstantial equivalent of the specifically recited number.

All publications, patents, and patent applications cited in thisspecification are incorporated herein by reference to the same extent asif each individual publication, patent, or patent application werespecifically and individually indicated to be incorporated by reference.Furthermore, each cited publication, patent, or patent application isincorporated herein by reference to disclose and describe the subjectmatter in connection with which the publications are cited. The citationof any publication is for its disclosure prior to the filing date andshould not be construed as an admission that the invention describedherein is not entitled to antedate such publication by virtue of priorinvention. Further, the dates of publication provided may be differentfrom the actual publication dates, which may need to be independentlyconfirmed.

It is noted that, as used herein and in the appended claims, thesingular forms “a”, “an”, and “the” include plural references unless thecontext clearly dictates otherwise. It is further noted that the claimsmay be drafted to exclude any optional element. As such, this statementis intended to serve as antecedent basis for use of such exclusiveterminology as “solely,” “only” and the like in connection with therecitation of claim elements, or use of a “negative” limitation.

As will be apparent to those of skill in the art upon reading thisdisclosure, each of the individual embodiments described and illustratedherein has features that may readily be separated from or combined withthe features of any of the other several embodiments without departingfrom the scope or spirit of the invention. For example, any recitedmethod may be carried out in the order of steps recited or in any otherorder. Although features similar or equivalent to those described hereinmay also be used in the practice or testing of the invention,representative components and features are described.

The invention described herein provides systems and methods directed topartially or completely removing from an industrial waste gas stream twoor more components of the waste gas stream, and compositions thatinclude two or more components or products of the two or more componentsof an industrial waste gas. In some cases, one of the components iscarbon dioxide, and the other component or components is one or more ofSOx, NOx, and a metal. In some of the systems and methods, removingcarbon dioxide and/or the other component or components occurs in singleprocessor or process. In some systems and methods of the invention, theindustrial waste gas stream may be pretreated. In some systems andmethods of the invention, the industrial waste gas stream in notpretreated. The composition may be a solution, a precipitation materialcomprising carbonates, bicarbonates, or carbonates and bicarbonates, ora slurry comprising a precipitation material. In some embodiments, thecomposition further comprises carbonate and/or bicarbonate co-productsresulting from co-processing SOx, NOx, particulate matter, and/orcertain metals. Additional waste streams such as liquid, solid, ormultiphasic waste streams may be processed as well.

In the following paragraphs is described a method of treating anindustrial waste gas, wherein the gas comprises carbon dioxide and atleast one other component selected from the group consisting of SOx;NOx; a metal; a non-carbon dioxide acid gas; an organic; and particulatematter, comprising contacting the gas with a liquid under conditionsadapted to cause at least some of the carbon dioxide and the othercomponent or components to exit the gas and enter the liquid, whereinthe method is carried out in a single processor.

In the following paragraphs is described a method comprising (i)contacting a gas stream with an aqueous solution, wherein the gas streamcomprises carbon dioxide and at least one other component selected fromthe group consisting of SOx; NOx; a metal; a non-carbon dioxide acidgas; an organic; and particulate matter, under conditions adapted tocause at least some of the carbon dioxide and the other component orcomponents to exit the gas stream and enter the aqueous solution; and(ii) processing the aqueous solution to produce a composition comprisingcarbonates, bicarbonates, or a combination of carbonates andbicarbonates, and the other component or a derivative thereof, or theother components and/or derivatives thereof, wherein the carbonates,bicarbonates, or the combination of carbonates and bicarbonates, is atleast partially derived from the carbon dioxide.

In the following paragraphs is described a composition produced by anyof the methods herein.

In the following paragraphs is described a composition comprisingcarbonates, bicarbonates, or a combination thereof, and asulfur-containing compound, wherein the carbonates, bicarbonates, orcombination thereof have a relative carbon isotope composition (δ¹³C)value less than −5.00‰, and wherein the composition, when subjected to aleaching process consisting essentially of preparing 2×1 L of anextraction fluid consisting essentially of an aqueous solution of aceticacid, wherein each 1 L of the extraction fluid consists essentially of5.7 mL acetic acid in deionized water; grinding the solid such thatparticles of ground solid are less than 1 cm in the narrowest dimensionif the particles are not already less than 1 cm in the narrowestdimension; placing 100 g of the ground solid into an extraction vesselwith 2 L of the extraction fluid to produce an extraction composition;rotating the extraction vessel in an end-over-end fashion for 18±2 hoursat room temperature; filtering the extraction composition throughborosilicate glass fiber with a pore size of 0.6 μm to 0.8 μm to producea leachate; and adjusting pH of the leachate with 1N nitric acid to a pHof pH 2 or less than pH 2, produces a leachate comprising less than 2.0mg/L of mercury.

In the following paragraphs is described a composition comprisingcarbonates, bicarbonates, or a combination thereof, and mercury, amercury derivative, or a combination thereof, wherein the carbonates,bicarbonates, or the combination thereof have a relative carbon isotopecomposition (δ¹³C) value less than −5.00‰, and wherein the composition,when subjected a leaching process consisting essentially of preparing2×1 L of an extraction fluid consisting essentially of an aqueoussolution of acetic acid, wherein each 1 L of the extraction fluidconsists essentially of 5.7 mL acetic acid in deionized water; grindingthe solid such that particles of ground solid are less than 1 cm in thenarrowest dimension if the particles are not already less than 1 cm inthe narrowest dimension; placing 100 g of the ground solid into anextraction vessel with 2 L of the extraction fluid to produce anextraction composition; rotating the extraction vessel in anend-over-end fashion for 18±2 hours at room temperature; filtering theextraction composition through borosilicate glass fiber with a pore sizeof 0.6 μm to 0.8 μm to produce a leachate; and adjusting pH of theleachate with 1N nitric acid to a pH of pH 2 or less than pH 2, producesa leachate comprising less than 2.0 mg/L of mercury. In someembodiments, the leachate comprises less than 1.5 mg/L of mercury.

In the following paragraphs is described a composition comprisingcarbonates, bicarbonates, or a combination thereof, mercury, a mercuryderivative, or a combination thereof, and sulfur-containing compound,wherein the composition, (i) when subjected to a leaching processconsisting essentially of preparing 2×1 L of an extraction fluidconsisting essentially of an aqueous solution of acetic acid, whereineach 1 L of the extraction fluid consists essentially of 5.7 mL aceticacid in deionized water; grinding the solid such that particles ofground solid are less than 1 cm in the narrowest dimension if theparticles are not already less than 1 cm in the narrowest dimension;placing 100 g of the ground solid into an extraction vessel with 2 L ofthe extraction fluid to produce an extraction composition; rotating theextraction vessel in an end-over-end fashion for 18±2 hours at roomtemperature; filtering the extraction composition through borosilicateglass fiber with a pore size of 0.6 μm to 0.8 μm to produce a leachate;and adjusting pH of the leachate with 1N nitric acid to a pH of pH 2 orless than pH 2, produces a leachate comprising less than 0.2 mg/L ofmercury; and (ii) when subjected to a carbon dioxide release protocolconsisting essentially of grinding the composition such that particlesof ground composition are less than 1 cm in the narrowest dimension ifthe particles are not already less than 1 cm in the narrowest dimensionand immersing the ground composition in a solution having a pH betweenpH 4.8 and pH 5.2 and a temperature between 60 and 80° C. for 48 hours,produces no more than 5 grams carbon dioxide per 100 grams composition.

In the following paragraphs is described a system comprising (i) asource of an industrial waste gas operably connected to (ii) a processorconfigured to (a) process the gas to at least partially remove carbondioxide from the gas and also to at least partially remove at least oneother component from the gas, wherein the other component is selectedfrom the group consisting of SOx, NOx, a metal, particulate matter, anon-carbon dioxide acid gas, and an organic and (b) produce acomposition comprising a product comprising at least a portion of thecarbon dioxide, or one or more derivatives thereof, in combination withat least a portion of the other component or one or more derivativesthereof, wherein the composition is suitable for placement in theenvironment.

In the following paragraphs is described a system comprising (i) asource of an industrial waste gas comprising carbon dioxide and one ormore other components selected from the group consisting of SOx, NOx, ametal, non-carbon dioxide acid gas, an organic, and particulate matter;(ii) a processor configured to remove at least a portion of the carbondioxide and the other component or components from the gas in a singleprocessing unit; and (iii) a conduit operably connecting the source ofindustrial waste gas and the processor, wherein the conduit isconfigured to direct at least a portion of the industrial waste gas tothe processor.

As such, in the following paragraphs is described systems and methodsfor processing waste gas streams comprising CO₂ and/or one or moreadditional components. Different feedstocks (e.g., industrial waste gasstreams, sources of proton-removing agents, sources of divalent cations)are also described, followed by compositions produced by systems andmethods of the invention.

In some embodiments, the invention provides a system for processingcarbon dioxide as shown in FIG. 1A, wherein the system comprises atleast one processor (110) configured for a liquid-based (e.g., anaqueous-based) process for processing carbon dioxide from a source ofcarbon dioxide (130) using a source of proton-removing agents (140), andwherein the source of carbon dioxide comprises one or more additionalcomponents in addition to carbon dioxide. As shown in FIG. 1A, thesystem may further comprise a source of divalent cations (150) operablyconnected to the processor. The processor may comprise a contactor suchas a gas-liquid or a gas-liquid-solid contactor, wherein the contactoris configured for charging an aqueous solution or slurry with carbondioxide to produce a carbon dioxide-charged composition, whichcomposition may be a solution or slurry. In some embodiments, thecontactor is configured to produce compositions from the carbon dioxide,such as from solvated or hydrated forms of carbon dioxide (e.g.,carbonic acid, bicarbonates, carbonates), wherein the compositionscomprise carbonates, bicarbonates, or carbonates and bicarbonates. Insome embodiments, the processor may further comprise a reactorconfigured to produce compositions comprising carbonates, bicarbonates,or carbonates and bicarbonates from the carbon dioxide. In someembodiments, the processor may further comprise a settling tankconfigured for settling compositions comprising precipitation materialcomprising carbonates, bicarbonates, or carbonates and bicarbonates. Asshown in FIG. 1B, the system may further comprise a treatment system(e.g., treatment system 120 of FIG. 1B) configured to concentratecompositions comprising carbonates, bicarbonates, or carbonates andbicarbonates and produce a supernatant; however, in some embodiments thecompositions are used without further treatment. For example, systems ofthe invention may be configured to directly use compositions from theprocessor (optionally with minimal post-processing) in the manufactureof building materials. In another non-limiting example, systems of theinvention may be configured to directly inject compositions from theprocessor (optionally with minimal post-processing) into a subterraneansite as described in U.S. Provisional Patent Application No. 61/232,401,filed 7 Aug. 2009, which is incorporated herein by reference in itsentirety. The source of carbon dioxide may be any of a variety ofindustrial sources of carbon dioxide, including, but not limited tocoal-fired power plants and cement plants. The source of proton-removingagents may be any of a variety of sources of proton-removing agents,including, but not limited to, natural sources of proton-removing agentsand industrial sources of proton-removing agents (including industrialwaste sources). The source of divalent cations may be from any of avariety of sources of divalent cations, including, but not limited to,seawater, brines, and freshwater with added minerals. In suchembodiments, the source of divalent cations may be operably connected tothe source of proton-removing agents or directly to the processor. Insome embodiments, the source of divalent cations comprises divalentcations of alkaline earth metals (e.g., Ca²⁺, Mg²⁺).

Systems of the invention such as that shown in FIG. 1A may furthercomprise a treatment system. As such, in some embodiments, the inventionprovides a system for processing carbon dioxide as shown in FIG. 1B,wherein the system comprises a processor (110) and a treatment system(120) configured for an aqueous-based process for processing carbondioxide from a source of carbon dioxide (130) using a source ofproton-removing agents (140), and wherein the source of carbon dioxidecomprises one or more additional components in addition to carbondioxide. As with FIG. 1A, the system of FIG. 1B may further comprise asource of divalent cations (150) operably connected to the processor.The processor may comprise a contactor such as a gas-liquid or agas-liquid-solid contactor, wherein the contactor is configured forcharging an aqueous solution or slurry with carbon dioxide to produce acarbon dioxide-charged composition, which composition may be a solutionor slurry. In some embodiments, the contactor is configured to producecompositions from the carbon dioxide, such as from solvated or hydratedforms of carbon dioxide (e.g., carbonic acid, bicarbonates, carbonates),wherein the compositions comprise carbonates, bicarbonates, orcarbonates and bicarbonates. In some embodiments, the processor mayfurther comprise a reactor configured to produce compositions comprisingcarbonates, bicarbonates, or carbonates and bicarbonates from the carbondioxide. In some embodiments, the processor may further comprise asettling tank configured for settling compositions comprisingprecipitation material comprising carbonates, bicarbonates, orcarbonates and bicarbonates. The treatment system may comprise adewatering system configured to concentrate compositions comprisingcarbonates, bicarbonates, or carbonates and bicarbonates. The treatmentsystem may further comprise a filtration system, wherein the filtrationsystem comprises at least one filtration unit configured for filtrationof supernatant from the dewatering system, filtration of the compositionfrom the processor, or a combination thereof. For example, in someembodiments, the filtration system comprises one or more filtrationunits selected from a microfiltration unit, an ultrafiltration unit, ananofiltration unit, and a reverse osmosis unit. In some embodiments,the carbon dioxide processing system comprises a nanofiltration unitconfigured to increase the concentration of divalent cations in theretentate and reduce the concentration of divalent cations in theretentate. In such embodiments, nanofiltration unit retentate may berecirculated to a processor of the system for producing compositions ofthe invention. As shown in FIG. 1D, systems of the invention may befurther configured to recirculate at least a portion of the supernatantfrom the treatment system.

Systems such as that shown in FIG. 1C may further comprise a processor(110) comprising a contactor (112) (e.g., gas-liquid contactor,gas-liquid-solid contactor, etc.) and a reactor (114), wherein theprocessor is operably connected to each of a source of CO₂-containinggas (130), a source of proton-removing agents (140), and a source ofdivalent cations (150). Such systems of the invention are configured foraqueous-based processing of carbon dioxide from the source of carbondioxide using both the source of proton-removing agents and the sourceof divalent cations, wherein the source of carbon dioxide comprises oneor more additional components in addition to carbon dioxide. Thecontactor (112) may be operably connected to each of the source ofcarbon dioxide (130) and the source of proton-removing agents (140), andthe contactor may be configured for charging an aqueous solution orslurry with carbon dioxide to produce a carbon dioxide-charged solutionor slurry. In some embodiments, the contactor is configured to charge anaqueous solution with carbon dioxide to produce a substantially clearsolution (i.e., substantially free of precipitation material, such as atleast 95% or more free). As shown in FIG. 1C, the reactor (114) may beoperably connected to the contactor (112) and the source of divalentcations (150), and the reactor may be configured to produce acomposition of the invention, wherein the composition is a solution orslurry comprising carbonates, bicarbonates, or carbonates andbicarbonates. In some embodiments, the reactor is configured to receivea substantially clear solution of carbonates, bicarbonates, orcarbonates and bicarbonates from the processor and produce a compositioncomprising precipitation material (e.g., a slurry of carbonates,bicarbonates, or carbonates and bicarbonates of divalent cations).Systems such as the one shown in FIG. 1C may optionally be operablyconnected to a treatment system, which treatment system may comprise aliquid-solid separator (122) or some other dewatering system configuredto treat processor-produced compositions to produce supernatant andconcentrated compositions (e.g., concentrated with respect to carbonatesand/or bicarbonates, and any other co-products resulting from processingan industrial waste gas stream). The treatment system may furthercomprise a filtration system, wherein the filtration system comprises atleast one filtration unit configured for filtration of supernatant fromthe dewatering system, filtration of the composition from the processor,or a combination thereof.

In some embodiments, the invention provides a system for processingcarbon dioxide as shown in FIG. 1D, wherein the system comprises aprocessor (110) and a treatment system (120) configured for anaqueous-based process for processing carbon dioxide from a source ofcarbon dioxide (130) using a source of proton-removing agents (140),wherein the source of carbon dioxide comprises one or more additionalcomponents in addition to carbon dioxide, and further wherein theprocessor and the treatment system are operably connected forrecirculating at least a portion of treatment system supernatant. Thetreatment system of such carbon dioxide-processing systems may comprisea dewatering system and a filtration system. As such, the dewateringsystem, the filtration system, or a combination of the dewatering systemand the filtration system may be configured to provide at least aportion of supernatant to the processor for processing carbon dioxide.Although not shown in FIG. 1D, the treatment system may also beconfigured to provide at least a portion of supernatant to a washingsystem configured to wash compositions of the invention, wherein thecompositions comprise precipitation material (e.g., CaCO₃, MgCO₃, orcombinations thereof). The processor of carbon dioxide-processingsystems of the invention may be configured to receive treatment systemsupernatant in a contactor (e.g., gas-liquid contactor, gas-liquid-solidcontactor), a reactor, a combination of the contactor and the reactor,or in any other unit or combination of units in the processor. In someembodiments, the carbon dioxide-processing system is configured toprovide at least a portion of the supernatant to a system or processexternal to the carbon-dioxide processing system. For example, a systemof the invention may be operably connected to a desalination plant suchthat the system provides at least a portion of treatment systemsupernatant to the desalination plant for desalination.

In some embodiments, the invention provides a system for processingcarbon dioxide as shown in FIG. 1E, wherein the system comprises aprocessor (110) and a treatment system (120) configured for anaqueous-based process for processing carbon dioxide from a source ofcarbon dioxide (130) using a source of proton-removing agents (140),wherein the source of carbon dioxide comprises one or more additionalcomponents in addition to carbon dioxide, wherein the system furthercomprises an electrochemical system (160), and further wherein theprocessor, the treatment system, and the electrochemical system areoperably connected for recirculating at least a portion of treatmentsystem supernatant. As described above in reference to the treatmentsystem of FIG. 1D, the dewatering system, the filtration system, or acombination of the dewatering system and the filtration system may beconfigured to provide at least a portion of treatment system supernatantto the processor for processing carbon dioxide. The treatment system mayalso be configured to provide at least a portion of the treatment systemsupernatant to the electrochemical system, wherein the electrochemicalsystem may be configured to produce proton-removing agents or effectproton removal. As described in reference to FIG. 1D, the treatmentsystem may also be configured to provide at least a portion ofsupernatant to a washing system configured to wash compositions of theinvention, wherein the compositions comprise precipitation material(e.g., CaCO₃, MgCO₃, or combinations thereof). The processor of carbondioxide-processing systems of the invention may be configured to receivetreatment system supernatant or an electrochemical system stream in acontactor (e.g., gas-liquid contactor, gas-liquid-solid contactor), areactor, a combination of the contactor and the reactor, or in any otherunit or combination of units in the processor. In some embodiments, thecarbon dioxide-processing system may be configured to provide at least aportion of the supernatant to a system (e.g., desalination plant) orprocess (e.g., desalination) external to the carbon-dioxide processingsystem.

In some embodiments, the invention provides a system for aqueous-basedprocessing of carbon dioxide as shown in FIG. 1F, wherein the system(100F) comprises a source of CO₂ (130), a source of proton-removingagents (140), a source of divalent cations (150), and a processor (110)comprising a gas-liquid or gas-liquid-solid contactor (112), arecirculation tank (116), a recirculation pump (118), and a reactor(114), wherein the contactor, recirculation tank, and recirculation pumpare operably connected for recirculating at least a portion of thecontactor liquid (e.g., solution or slurry of carbonates, bicarbonates,or carbonates and bicarbonates). As shown in FIG. 1F, the system mayfurther comprise a treatment system (120) comprising a dewatering systemand/or a filtration system, wherein the treatment system is configuredto provide a supernatant and a concentrated composition of the invention(e.g., dewatered precipitation material comprising carbonates,bicarbonates, or carbonates and bicarbonates). Such systems may alsooptionally comprise emission control technology such as an electrostaticprecipitator or a fabric filter configured for separating particulatematter (e.g., fly ash) from flue gas. While system elements may vary asdescribed herein, in a non-limiting example the source of CO₂ (130) forsystems such as system 100F may be a coal-fired combustor, the source ofproton-removing agents may be a tank or reservoir comprising a mixtureof NaOH or Na₂CO₃ in freshwater or seawater, and the source of divalentcations may be a tank or reservoir comprising seawater or brine (e.g.,synthetic brine). An exemplary method of using the system of FIG. 1F isprovided in Example 1; however, one of ordinary skill in the art willrecognize that various methods described herein may be used with thesystem of FIG. 1F.

In reference to FIG. 1A, the invention provides an aqueous-based methodfor processing a source of carbon dioxide (130) and producing acomposition comprising carbonates, bicarbonates, or carbonates andbicarbonates, wherein the source of carbon dioxide comprises one or moreadditional components in addition to carbon dioxide. In suchembodiments, the industrial source of carbon dioxide may be sourced, asource of proton-removing agents (140) may be sourced, and each may beprovided to processor 110 to be processed (i.e., subjected to suitableconditions for production of the composition comprising carbonates,bicarbonates, or carbonates and bicarbonates). In some embodiments,processing the industrial source of carbon dioxide comprises contactingthe source of proton-removing agents in a contactor such as, but notlimited to, a gas-liquid contactor or a gas-liquid-solid contactor toproduce a carbon dioxide-charged composition, which composition may be asolution or slurry, from an initial aqueous solution or slurry. In someembodiments, the composition comprising carbonates, bicarbonates, orcarbonates and bicarbonates may be produced from the carbondioxide-charged solution or slurry in the contactor. In someembodiments, the carbon dioxide-charged solution or slurry may beprovided to a reactor, within which the composition comprisingcarbonates, bicarbonates, or carbonates and bicarbonates may beproduced. In some embodiments, the composition is produced in both thecontactor and the reactor. For example, in some embodiments, thecontactor may produce an initial composition comprising bicarbonates andthe reactor may produce the composition comprising carbonates,bicarbonates, or carbonates and bicarbonates from the initialcomposition. In some embodiments, methods of the invention may furthercomprise sourcing a source of divalent cations such as those of alkalineearth metals (e.g., Ca²⁺, Mg²⁺). In such embodiments, the source ofdivalent cations may be provided to the source of proton-removing agentsor provided directly to the processor. Provided sufficient divalentcations are provided by the source of proton-removing agents, by thesource of divalent cations, or by a combination of the foregoingsources, the composition comprising carbonates, bicarbonates, orcarbonates and bicarbonates may comprise an isolable precipitationmaterial (e.g., CaCO₃, MgCO₃, or a composition thereof). Whether thecomposition from the processor comprises an isolable precipitationmaterial or not, the composition may be used directly from the processor(optionally with minimal post-processing) in the manufacture of buildingmaterials. In some embodiments, compositions comprising carbonates,bicarbonates, or carbonates and bicarbonates directly from the processor(optionally with minimal post-processing) may be injected into asubterranean site as described in U.S. Provisional Patent ApplicationNo. 61/232,401, filed 7 Aug. 2009, which application is incorporatedherein by reference in its entirety.

In reference to FIGS. 1B-1E, the invention provides an aqueous-basedmethod for processing a source of carbon dioxide (130) and producing acomposition comprising carbonates, bicarbonates, or carbonates andbicarbonates, wherein the source of carbon dioxide comprises one or moreadditional components in addition to carbon dioxide. In addition toproducing compositions as described in reference to FIG. 1A, theinvention further provides methods for treating compositions comprisingcarbonates, bicarbonates, or carbonates and bicarbonates. As such, insome embodiments, the invention provides an aqueous-based method forprocessing a source of carbon dioxide (130) to produce a compositioncomprising carbonates, bicarbonates, or carbonates and bicarbonates andtreating the composition produced. Whether a processor-producedcomposition of the invention comprises an isolable precipitationmaterial or not, the composition may be directly provided to a treatmentsystem of the invention for treatment (e.g., concentration, filtration,etc.). In some embodiments, the composition may be provided directly tothe treatment system from a contactor, a reactor, or a settling tank ofthe processor. For example, a processor-produced composition that doesnot contain an isolable precipitation material may be provided directlyto a treatment system for concentration of the composition andproduction of a supernatant. In another non-limiting example, aprocessor-produced composition comprising an isolable precipitationmaterial may be provided directly to a treatment system for liquid-solidseparation. The processor-produced composition may be provided to any ofa number of treatment system sub-systems, which sub-systems include, butare not limited to, dewatering systems, filtration systems, ordewatering systems in combination with filtration systems, whereintreatment systems, or a sub-systems thereof, separate supernatant fromthe composition to produce a concentrated composition (e.g., theconcentrated composition is more concentrated with to respect tocarbonates, bicarbonates, or carbonates and carbonates).

With reference to FIG. 1C, in some embodiments, the invention provides amethod for charging a solution with CO₂ from an industrial waste gasstream to produce a composition comprising carbonates, bicarbonates, orcarbonates and bicarbonates. In such embodiments, the solution may havea pH ranging from pH 6.5 to pH 14.0 prior to charging the solution withCO₂. In some embodiments, the solution may have a pH of at least pH 6.5,pH 7.0, pH 7.5, pH 8.0, pH 8.5, pH 9.0, pH 9.5, pH 10.0, pH 10.5, pH11.0, pH 11.5, pH 12.0, pH 12.5, pH 13.0, pH 13.5, or pH 14.0 prior tocharging the solution with CO₂. The pH of the solution may be increasedusing any convenient approach including, but not limited to, use ofproton-removing agents and electrochemical methods for effecting protonremoval. In some embodiments, proton-removing agents may be used toincrease the pH of the solution prior to charging the solution with CO₂.Such proton-removing agents include, but are not limited to, hydroxides(e.g., NaOH, KOH) and carbonates (e.g., Na₂CO₃. K₂CO₃). In someembodiments, sodium hydroxide is used to increase the pH of thesolution. As such, in some embodiments, the invention provides a methodfor charging an alkaline solution (e.g., pH>pH 7.0) with CO₂ from anindustrial waste gas stream to produce a composition comprisingcarbonates, bicarbonates, or carbonates and bicarbonates.

In some embodiments, the composition resulting from charging thealkaline solution with CO₂ from an industrial waste source (i.e., thesolution comprising carbonates, bicarbonates, or carbonates andbicarbonates) may be a slurry or a substantially clear solution (i.e.,substantially free of precipitation material, such as at least 95% ormore free) depending upon the cations available in the solution at thetime the solution is charged with CO₂. As described herein, the solutionmay, in some embodiments, comprise divalent cations such as Ca²⁺, Mg²⁺,or a combination thereof at the time the solution is charged with CO₂.In such embodiments, the resultant composition may comprise carbonates,bicarbonates, or carbonates and bicarbonates of divalent cations (e.g.precipitation material) resulting in a slurry. Such slurries, forexample, may comprise CaCO₃, MgCO₃, or a combination thereof. Thesolution may, in some embodiments, comprise insufficient divalentcations to form a slurry comprising carbonates, bicarbonates, orcarbonates and bicarbonates of divalent cations at the time the solutionis charged with CO₂. In such embodiments, the resultant composition maycomprise carbonates, bicarbonates, or carbonates and bicarbonates in asubstantially clear solution (i.e., substantially free of precipitationmaterial, such as at least 95% or more free) at the time the solution ischarged with CO₂. In some embodiments, for example, monovalent cationssuch as Na⁺, K⁺, or a combination thereof (optionally by addition ofNaOH and/or KOH) may be present in the substantially clear solution atthe time the solution is charged with CO₂. The composition resultingfrom charging such a solution with CO₂ may comprise, for example,carbonates, bicarbonates, or carbonates and bicarbonates of monovalentcations.

As such, in some embodiments, the invention provides a method forcharging an alkaline solution (e.g., pH>pH 7.0) with CO₂ from anindustrial waste gas stream to produce a composition comprisingcarbonates, bicarbonates, or carbonates and bicarbonates, wherein thecomposition is substantially clear (i.e., substantially free ofprecipitation material, such as at least 95% or more free). Thesubstantially clear composition may subsequently be contacted with asource of divalent cations (e.g., Ca²⁺, Mg²⁺, or a combination thereof)to produce a composition comprising carbonates, bicarbonates, orcarbonates and bicarbonates of divalent cations resulting in a slurry.As above, such slurries may comprise CaCO₃, MgCO₃, or a combinationthereof that may be treated as described herein. In a non-limitingexample, an alkaline solution comprising NaOH (e.g., NaOH dissolved infreshwater lacking significant divalent cations) may be contacted in agas-liquid contactor with CO₂ from an industrial waste gas stream toproduce a composition comprising carbonates, bicarbonates, or carbonatesand bicarbonates, wherein the composition is substantially clear due toa lack of precipitation material, which, in turn, is due to the lack ofsignificant divalent cations. Depending upon the amount of CO₂ added(and makeup NaOH, if any), the substantially clear composition maycomprise NaOH, NaHCO₃, and/or Na₂CO₃. The substantially clearcomposition may subsequently be contacted in a reactor outside thegas-liquid contactor with a source of divalent cations (e.g., Ca²⁺,Mg²⁺, Sr²⁺, and the like) to produce a composition comprisingcarbonates, bicarbonates, or carbonates and bicarbonates of divalentcations (e.g., precipitation material) resulting in a slurry. As such,compositions may comprise CaCO₃ and/or MgCO₃, and the compositions maybe treated as described herein. For example, the composition may besubjected to liquid-solid separation and the solids manufactured intocement, supplementary cementitious material, fine aggregate, mortar,coarse aggregate, concrete, pozzolan, or a combination thereof.

With reference to FIGS. 1D and 1E, the invention also providesaqueous-based methods of processing a source of carbon dioxide (130) andproducing a composition comprising carbonates, bicarbonates, orcarbonates and bicarbonates, wherein the source of carbon dioxidecomprises one or more additional components in addition to carbondioxide, and wherein at least a portion of treatment system supernatantis recirculated. For example, in some embodiments, the inventionprovides a method of treating a waste gas stream comprising CO₂ and SOx,NOx, and/or Hg in a processer to produce a processed waste gas stream(e.g., a clean gas stream suitable for release into the environment inaccordance with Reasonably Available Control Technology (RACT); BestAvailable Control Technology (BACT); Maximum Achievable ControlTechnology (MACT); Lowest Achievable Emission Rate (LAER); and/or anyUnited States Environmental Protection Agency (EPA) reference methods,as such emission control standards exist on the filing date of thispatent application.), a composition comprising carbonates, bicarbonates,or carbonates and bicarbonates, and an effluent, wherein at least aportion of the effluent is recirculated to the processor. As shown inFIGS. 1D and 1E, supernatant from the treatment system, which maycomprise a dewatering system and a filtration system, may berecirculated in a variety of ways. As such, in some embodiments, atleast a portion of the supernatant from the dewatering system, thefiltration system, or a combination of the dewatering system and thefiltration system may be used to process carbon dioxide. The supernatantmay be provided to a carbon dioxide-processing system processor. In suchembodiments, the supernatant may be provided to a contactor (e.g.,gas-liquid contactor, gas-liquid-solid contactor), to a reactor, to acombination of the contactor and the reactor, or to any other unit orcombination of units for processing carbon dioxide. In addition, in someembodiments, at least a portion of the supernatant from the treatmentsystem may be provided to a washing system. In such embodiments, thesupernatant may be used to wash compositions (e.g., precipitationmaterial comprising CaCO₃, MgCO₃, or a combination thereof) of theinvention. For example, the supernatant may be used to wash chloridefrom carbonate-based precipitation material. With reference to FIG. 1E,at least a portion of the treatment system supernatant may be providedto an electrochemical system. As such, treatment system supernatant maybe used to produce proton-removing agents or effect proton removal forprocessing carbon dioxide. In some embodiments, at least a portion ofthe supernatant from the treatment system may be provided to a differentsystem or process. For example, at least a portion of the treatmentsystem supernatant may be provided to a desalination plant ordesalination process such that the treatment system supernatant, whichis generally softer (i.e., lower concentration of Ca²⁺ and/or Mg²⁺) thanother available feeds (e.g., seawater, brine, etc.) after being used toprocess carbon dioxide, may be desalinated for potable water.

Recirculation of treatment system supernatant is advantageous asrecirculation provides efficient use of available resources; minimaldisturbance of surrounding environments; and reduced energyrequirements, which reduced energy requirements provide for lower carbonfootprints for systems and methods of the invention. When a carbondioxide-processing system of the invention is operably connected to anindustrial plant (e.g., fossil fuel-fired power plant such as coal-firedpower plant) and utilizes power generated at the industrial plant,reduced energy requirements provided by recirculation of treatmentsystem supernatant provide for a reduced parasitic load on theindustrial plant. A carbon dioxide-processing system not configured forrecirculation (i.e., a carbon-dioxide processing system configured for aonce-through process) such as that shown in FIG. 1B, may have aparasitic load on the industrial plant of at least 10% attributable tocontinuously pumping a fresh source of alkalinity (e.g., seawater,brine) into the system. In such an example, a 100 MW power plant (e.g.,a coal-fired power plant) would need to devote 10 MW of power to thecarbon dioxide-processing system for continuously pumping a fresh sourceof alkalinity into the system. In contrast, a system configured forrecirculation such as that shown in FIG. 1D or FIG. 1E may have aparasitic load on the industrial plant of less than 10%, such as lessthan 8%, including less than 6%, for example, less than 4% or less than2%, which parasitic load may be attributable to pumping make-up waterand recirculating supernatant. Carbon dioxide-processing systemsconfigured for recirculation, may, when compared to systems designed fora once-through process, exhibit a reduction in parasitic load of atleast 2%, such as at least 5%, including at least 10%, for example, atleast 25% or at least 50%. For example, if a carbon dioxide-processingsystem configured for recirculation consumes 9 MW of power for pumpingmake-up water and recirculating supernatant and a carbondioxide-processing system designed for a once-through process consumes10 MW attributable to pumping, then the carbon dioxide-processing systemconfigured for recirculation exhibits a 10% reduction in parasitic load.For systems such as those shown in FIGS. 1D and 1E (i.e., carbondioxide-processing systems configured for recirculation), the reductionin the parasitic load attributable to pumping and recirculating may alsoprovide a reduction in total parasitic load, especially when compared tocarbon dioxide-processing systems configured for once-through process.In some embodiments, recirculation provides a reduction in totalparasitic load of a carbon dioxide-processing system, wherein thereduction is at least 2%, such as at least 4%, including at least 6%,for example at least 8% or at least 10% when compared to total parasiticload of a carbon dioxide-processing system configured for once-throughprocess. For example, if a carbon dioxide-processing system configuredfor recirculation has a 15% parasitic load and a carbondioxide-processing system designed for a once-through process has a 20%parasitic load, then the carbon dioxide-processing system configured forrecirculation exhibits a 5% reduction in total parasitic load. Forexample, a carbon dioxide-processing system configured forrecirculation, wherein recirculation comprises filtration through afiltration unit such as a nanofiltration unit (e.g., to concentratedivalent cations in the retentate and reduce divalent cations in thepermeate), may have a reduction in total parasitic load of at least 2%,such as at least 4%, including at least 6%, for example at least 8% orat least 10% when compared to a carbon dioxide-processing systemconfigured for once-through process.

The parasitic load of carbon dioxide-processing systems of the inventionmay be further reduced by efficient use of other resources. In someembodiments, the parasitic load of carbon dioxide-processing systems ofthe invention may be further reduced by efficient use of heat from anindustrial source. In some embodiments, for example, heat from theindustrial source of carbon dioxide (e.g., flue gas heat from acoal-fired power plant) may be utilized for drying a compositioncomprising precipitation material comprising carbonates, bicarbonates,or carbonates and bicarbonates. In such embodiments, a spray dryer maybe used for spray drying the composition. For example, low-grade (e.g.,150-200° C.) waste heat may be utilized by means of a heat exchanger toevaporatively spray dry the composition comprising the precipitationmaterial. In addition, utilizing heat from the industrial source ofcarbon dioxide for drying compositions of the invention allows forsimultaneous cooling of the industrial source of carbon dioxide (e.g.,flue gas from a coal-fired power plant), which enhances dissolution ofcarbon dioxide, a process which is inversely related to temperature. Insome embodiments, the parasitic load of carbon dioxide-processingsystems of the invention may be further reduced by efficient use ofpressure. For example, in some embodiments, carbon dioxide-processingsystems of the invention are configured with an energy recovery system.Such energy recovery systems are known, for example, in the art ofdesalination and operate by means of pressure exchange. In someembodiments, the overall parasitic load of the carbon dioxide-processingsystem may be less than 99.9%, 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%,15%, 10%, 5%, or 3% when capturing and processing 70-90% of the carbondioxide emitted from an industrial plant (e.g., coal-fired power plant).For example, in some embodiments, the overall parasitic load of thecarbon dioxide-processing system may be less than 30%, such as less than20%, including less than 15%, for example, less than 10%, less than 5%,or less than 3% when capturing and processing 70-90% of the carbondioxide emitted from an industrial plant (e.g., coal-fired power plant).As such, carbon dioxide-processing systems of the invention configuredfor recirculation, heat exchange, and/or pressure exchange may reducethe parasitic load on power-providing industrial plants whilemaintaining carbon dioxide processing capacity.

Inevitably, recirculation and other methods described herein consumewater as water may become part of a composition of the invention (e.g.,precipitation material comprising, for example, amorphous calciumcarbonate CaCO₃.H₂O; nesquehonite MgCO₃.2H₂O; etc.), may be vaporized bydrying (e.g., spray drying) compositions of the invention, or lost insome other part of the process. As such, make-up water may be providedto account for water lost to processing carbon dioxide to producecompositions of the invention (e.g., spray-dried precipitationmaterial). For example, make-up water amounting to less than 700,000gallons per day may replace water lost to producing, for example,spray-dried precipitation material from flue gas from a 35 MWecoal-fired power plant. Processes requiring only make-up water may beconsidered zero process water discharge processes. In processes in whichadditional water other than make-up water is used, that water may besourced from any of the water sources (e.g., seawater, brine, etc.)described herein. In some embodiments, for example, water may be sourcedfrom the power plant cooling stream and returned to that stream in aclosed loop system. Processes requiring make-up water and additionalprocess water are considered low process water discharge processesbecause systems and methods of the invention are designed to efficientlyuse resources.

Source of Carbon Dioxide

In some embodiments, the invention provides for contacting a volume ofan aqueous solution with a source of carbon dioxide to produce acomposition comprising carbonates, bicarbonates, or carbonates andbicarbonates, wherein the composition is a solution or slurry. In someembodiments, the solution is a slurry comprising a precipitationmaterial comprising carbonates, bicarbonates, or carbonates andbicarbonates. There may be sufficient carbon dioxide in the aqueoussolution to produce significant amounts of carbonates, bicarbonates, orcarbonates and bicarbonates (e.g., from brine or seawater); however,additional carbon dioxide is generally used. The source of CO₂ may beany convenient CO₂ source. The source of CO₂ may be a gas, a liquid, asolid (e.g., dry ice), a supercritical fluid, or CO₂ dissolved in aliquid. In some embodiments, the CO₂ source is a gaseous CO₂ source suchas a waste gas stream. The gaseous CO₂ source may be substantially pureCO₂ or, as described in more detail below, comprise one or morecomponents in addition to CO₂, wherein the one or more componentscomprise one or more additional gases (e.g., SOx, NOx), non-gaseouscomponents (e.g., particulate matter such as fly ash), or a combinationthereof. In some embodiments, the gaseous CO₂ source may be a waste gasstream (e.g., exhaust) produced by an active process of an industrialplant. The nature of the industrial plant may vary, the industrialplants including, but not limited to, power plants, chemical processingplants, mechanical processing plants, refineries, cement plants, steelplants, and other industrial plants that produce CO₂ as a by-product offuel combustion or another processing step (e.g., calcination by acement plant). In some embodiments, for example, the gaseous CO₂ sourcemay be flue gas from coal-fired power plant.

The gaseous waste stream may be provided by the industrial plant to theCO₂-processing system of the invention in any convenient manner thatconveys the gaseous waste stream. In some embodiments, the waste gasstream is provided with a gas conveyor (e.g., a duct, pipe, etc.) thatruns from a flue or analogous structure of the industrial plant (e.g., aflue of the industrial plant) to one or more locations of theCO₂-processing system. In such embodiments, a line (e.g., a duct, pipe,etc.) may be connected to the flue of the industrial plant such that gasleaving through the flue is conveyed to the appropriate location(s) ofthe CO₂-processing system (e.g., processor or a component thereof, suchas a gas-liquid contactor or gas-liquid-solid contactor). Depending uponthe particular configuration of the CO₂-processing system, the locationof the gas conveyor on the industrial plant may vary, for example, toprovide a waste gas stream of a desired temperature. As such, in someembodiments, where a gaseous waste stream having a temperature rangingfor 0° C. to 2000° C., such as 0° C. to 1800° C., including 60° C. to700° C., for example, 100° C. to 400° C. is desired, the flue gas may beobtained at the exit point of the boiler, gas turbine, kiln, or at anypoint of the power plant that provides the desired temperature. The gasconveyor may be configured to maintain flue gas at a temperature abovethe dew point (e.g., 125° C.) in order to avoid condensation and relatedcomplications. Other steps may be taken to reduce the adverse impact ofcondensation and other deleterious effects, such as employing ductingthat is stainless steel or fluorocarbon (such aspoly(tetrafluoroethylene)) lined such the duct does not rapidlydeteriorate.

Waste gas streams comprising CO₂ include both reducing condition streams(e.g., syngas, shifted syngas, natural gas, hydrogen, and the like) andoxidizing condition streams (e.g., flue gas resulting from combustion).Particular waste gas streams that may be convenient for the inventioninclude oxygen-containing flue gas resulting from combustion (e.g., fromcoal or another carbon-based fuel with little or no pretreatment of theflue gas), turbo charged boiler product gas, coal gasification productgas, pre-combustion synthesis gas (e.g., such as that formed during coalgasification in power generating plants), shifted coal gasificationproduct gas, anaerobic digester product gas, wellhead natural gasstream, reformed natural gas or methane hydrates, and the like.Combustion gas from any convenient source may be used in methods andsystems of the invention. In some embodiments, a combustion gas from apost-combustion effluent stack of an industrial plant such as a powerplant, cement plant, and coal processing plant is used.

Thus, waste gas streams may be produced from a variety of differenttypes of industrial plants. Suitable waste gas streams for the inventioninclude waste gas streams produced by industrial plants that combustfossil fuels (e.g., coal, oil, natural gas, propane, diesel) andanthropogenic fuel products of naturally occurring organic fuel deposits(e.g., tar sands, heavy oil, oil shale, etc.). In some embodiments, awaste gas stream suitable for systems and methods of the invention maybe sourced from a coal-fired power plant, such as a pulverized coalpower plant, a supercritical coal power plant, a mass burn coal powerplant, a fluidized bed coal power plant. In some embodiments, the wastegas stream is sourced from gas or oil-fired boiler and steam turbinepower plants, gas or oil-fired boiler simple cycle gas turbine powerplants, or gas or oil-fired boiler combined cycle gas turbine powerplants. In some embodiments, waste gas streams produced by power plantsthat combust syngas (i.e., gas that is produced by the gasification oforganic matter, for example, coal, biomass, etc.) are used. In someembodiments, waste gas streams from integrated gasification combinedcycle (IGCC) plants are used. In some embodiments, waste gas streamsproduced by heat recovery steam generator (HRSG) plants are used inaccordance with systems and methods of the invention.

Waste gas streams produced by cement plants are also suitable forsystems and methods of the invention. Cement plant waste gas streamsinclude waste gas streams from both wet process and dry process plants,which plants may employ shaft kilns or rotary kilns, and may includepre-calciners. These industrial plants may each burn a single fuel, ormay burn two or more fuels sequentially or simultaneously. Otherindustrial plants such as smelters and refineries are also usefulsources of waste gas streams that include carbon dioxide.

Carbon dioxide may be the primary non-air derived component in waste gasstreams. In some embodiments, waste gas streams may comprise carbondioxide in amounts ranging from 200 ppm to 1,000,000 ppm, such as200,000 ppm to 1000 ppm and including 200,000 ppm to 2000 ppm, forexample 130,000 ppm to 2000 ppm, wherein the amounts of carbon dioxidemay be considered time-averaged amounts. For example, in someembodiments, waste gas streams may comprise carbon dioxide in an amountranging from 40,000 ppm (4%) to 100,000 ppm (10%) depending on the wastegas stream (e.g., CO₂ from natural gas-fired power plants, furnaces,small boilers, etc.). For example, in some embodiments, waste gasstreams may comprise carbon dioxide in an amount ranging from 100,000ppm (10%) to 150,000 ppm (15%) depending on the waste gas stream (e.g.,CO₂ from coal-fired power plants, oil generators, diesel generators,etc.). For example, in some embodiments, waste gas streams may comprisecarbon dioxide in an amount ranging from 200,000 ppm (20%) to 400,000ppm (40%) depending on the waste gas stream (e.g., CO₂ from cement plantcalcination, chemical plants, etc.). For example, in some embodiments,waste gas streams may comprise carbon dioxide in an amount ranging from900,000 ppm (90%) to 1,000,000 ppm (100%) depending on the waste gasstream (e.g., CO₂ from ethanol fermenters, CO₂ from steam reforming atrefineries, ammonia plants, substitute natural gas (SNG) plants, CO₂separated from sour gases, etc.). The concentration of CO₂ in a wastegas stream may be decreased by 10% or more, 20% or more, 30% or more,40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 90% ormore, 95% or more, 99% or more, 99.9% or more, or 99.99%. In otherwords, at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 99%,99.9%, or 99.99% of the carbon dioxide may be removed from the waste gasstream.

A portion of the waste gas stream (i.e., not the entire gaseous wastestream) from an industrial plant may be used to produce compositionscomprising carbonates, bicarbonates, or carbonates and bicarbonates. Inthese embodiments, the portion of the waste gas stream that is employedin producing compositions may be 75% or less, such as 60% or less, andincluding 50% and less of the waste gas stream. In yet otherembodiments, most (e.g., 80% or more) of the entire waste gas streamproduced by the industrial plant is employed in producing compositions.In these embodiments, 80% or more, such as 90% or more, including 95% ormore, up to 100% of the waste gas stream (e.g., flue gas) generated bythe source may be employed for producing compositions of the invention.

Although a waste gas stream from an industrial plant offers a relativelyconcentrated source of CO₂ and/or additional components resulting fromcombustion of fossil fuels, methods and systems of the invention arealso applicable to removing combustion gas components from lessconcentrated sources (e.g., atmospheric air), which contains a muchlower concentration of pollutants than, for example, flue gas. Thus, insome embodiments, methods and systems encompass decreasing theconcentration of CO₂ and/or additional components in atmospheric air byproducing compositions of the invention. As with waste gas streams, theconcentration of CO₂ in a portion of atmospheric air may be decreased by10% or more, 20% or more, 30% or more, 40% or more, 50% or more, 60% ormore, 70% or more, 80% or more, 90% or more, 95% or more, 99% or more,99.9% or more, or 99.99%. Such decreases in CO₂ may be accomplished withyields as described herein, or with higher or lower yields, and may beaccomplished in one processing step or in a series of processing steps.

Other Components of Waste Gas Streams

Waste gas streams suitable for the invention may further comprise one ormore additional components including water; sulfur oxides (SOx);nitrogen oxides (NOx); carbon monoxide (CO); metals such as antimony(Sb), arsenic (As), barium (Ba), beryllium (Be), boron (B), cadmium(Cd), chromium (Cr), cobalt (Co), copper (Cu), lead (Pb), manganese(Mn), mercury (Hg), molybdenum (Mo), nickel (Ni), radium (Ra), selenium(Se), silver (Ag), strontium (Sr), thallium (Tl), vanadium (V), and zinc(Zn), wherein the metals may be in any available form including, but notlimited to, an elemental form (e.g., Hg⁰), a salt (e.g., HgCl₂), aninorganic compound (e.g., HgO), an organic compound (e.g., anorganomercury compound), or particulate form (e.g., Hg(p)); particulatematter (suspended particles of solids or liquids) such as fly ash, dust(e.g., from calcining), and metals; halides such as hydrogen chlorideand hydrogen fluoride, which may also be considered acid gases alongwith, for example, SOx (e.g., SO₃, SO₂); organics such as volatileorganic compounds (VOCs), hydrocarbons, dioxins, and polyaromatichydrocarbons (PAHs); toxic substances such as hydrogen cyanide andsulfur nitrate (SNO₃); and radioactive isotopes such as uranium (U) andthorium (Th), any one or more (e.g., two or more, three or more, four ormore, five or more, etc.) of which may be sequestered in a compositionof the invention. In some embodiments, the invention provides for atleast 1%, 5%, 10%, 25%, 30%, 40%, 50%, 60%, 70%, 75%, 80%, 85%, 90%,95%, 96%, 97%, 98%, 99%, 99.9%, or 99.99% removal of one or more of theadditional waste gas stream components, wherein each of the one or morecomponents may be removed at the same or a different percentage level.For example, in some embodiments, 98% of the SOx and 95% of the mercurymay be removed from a waste gas stream using systems and methods of theinvention, while, in other embodiments, 98% of the SOx and 98% of themercury may be removed from the waste gas stream. In another exemplaryembodiment, at least 99% SO₂, at least 88% SO₃, and 81% HCl, each ofwhich may be considered an acid gas, may be removed from a waste gasstream using systems and methods of the invention. In such anembodiment, the invention provides for at least 80% removal of acidgases (e.g., SOx, HCl, etc.). In addition to the foregoing, at least10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%,99.9%, or 99.99% of the carbon dioxide may be removed from the waste gasstream.

In a typical untreated flue gas resulting from combustion of alow-sulfur Eastern bituminous coal, the flue gas may comprise H₂O(5-7%); O₂ (3-4%); CO₂ (15-16%); Hg (1 ppb); CO (20 ppm); hydrocarbons(10 ppm); HCl (100 ppm); SOx (810 ppm, wherein the concentration of SO₂is 800 ppm and the concentration of SO₃ is 10 ppm); NOx (500 ppm,wherein the concentration of NO is 475 ppm and the concentration of NO₂is 25 ppm), and N₂ (balance). Different coals may give untreated fluegases with different contaminant concentrations (e.g., 10-15% CO₂, 10-20ppm CO, 500-3000 ppm SOx, 150-500 ppm NOx, 1-2 ppb Hg, 5-10% fly ash,etc.), any of which flue gases are suitable for use in the invention. Inreference to the medium (e.g., aqueous solution) in which CO₂ isprocessed, many of the additional components of waste gas streams may beconveniently, though not strictly, grouped as soluble (e.g., HgCl₂, NO₂,etc.), reactive (e.g., HCl, HF, etc.), or not soluble and not reactive(e.g., As, Cd, Pb, Cr, V, Se, etc.). Methods of the invention includetreating waste gas streams such that certain additional components maybe more soluble or more reactive in the medium in which CO₂ isprocessed. For example, in some embodiments, elemental mercury may beoxidized to mercuric chloride (HgCl₂) in the presence of hydrogenchloride (HCl) or chlorine (Cl₂), each of which may be generated byelectrochemical methods of the invention. This was serendipitouslydiscovered upon practice of the invention when burning various coalshaving different chlorine contents. Coal having more chlorine content,it was discovered, makes for better capture of various mercury species,particularly divalent mercury (Hg²⁺).

Sulfur oxides (SOx) may refer to any of lower sulfur oxides such as SO,S₂O₂, S₂O, S₃O, S_(x)O (where x is 5-10), S₆O₂, S₇O₂, and polymericsulfuroxides; sulfur monoxide (SO); sulfur dioxide (SO₂); sulfurtrioxide (SO₃); and higher sulfur oxides such as SO_(3+y) (where 0<y≦1),or a combination thereof. The combustion of coal, oil, natural gas, orany other sulfur-containing fuels may produce a flue gas in which 98-99%of the sulfur is in the form of sulfur dioxide (SO₂) and 1-2% is sulfurtrioxide (SO₃). For low and high sulfur coals the total concentration ofSOx may be in the range of 1,000-4,000 ppm. The invention provideshighly efficient desulfurization of waste gas streams, utilizing anaqueous solution (e.g., seawater, brine, etc.) and, optionally, a sourceof proton-removing agents such as industrial waste (e.g., fly ash, CKD,brucite tailings, etc.). In some embodiments, the invention provides forat least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%,70%, 75%, 80%, 85%, 90%, 95%, or 99.9% removal of SOx from a waste gasstream. In such embodiments, SOx removal may directly result fromprocessing the waste gas stream in a processor of the invention withoutadditional SOx control technology. In some embodiments, such SOx removalmay result from a combination of processing the waste gas stream in aprocessor of the invention and using a desulfurization technology. Suchdesulfurization technologies include, but are not limited to, wetscrubbing, spray-dry scrubbing, wet sulfuric acid process (WSA), and drysorbent injection systems. Desulfurization of waste gas streamsutilizing a processor of the invention may result in incorporation of,for example, calcium sulfate into precipitation material of theinvention, which may then be used for various applications in the builtenvironment. In some embodiments, forced oxidation may be used tooxidize sulfur compounds in the waste gas stream or in solution (e.g.,sulfites to sulfates) to produce sulfates for incorporation intoprecipitation material. For example, in some embodiments, SO₂ may beabsorbed in a solution as sulfite, which, in turn, may be converted tosulfate by oxidation through aeration. In some embodiments, SO₂ may beconverted to sulfite upon contact with a solution (e.g., solution ofproton-removing agents and/or divalent cations), which sulfite may beoxidized under conditions already existing in the solution. In suchembodiments, sulfate may present in precipitation material of theinvention, supernatant resulting from separation of the precipitationmaterial, or both the precipitation material and the supernatant.

Nitrogen oxides may refer to any of NO and NO₂, or a combinationthereof, and may be produced during combustion of coal, oil, and otherfuels, especially during high-temperature combustion. NOx is mainlyproduced in the form of nitric oxide (NO). Some nitrogen dioxide (NO₂)is also formed, but its concentration may be less than 5% of the totalNOx concentration, which is typically 200-1000 ppm. In some embodiments,the invention provides for at least 5%, 10%, 15%, 20%, 25%, 30%, 35%,40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 99.9%removal of NOx from a waste gas stream. In such embodiments, NOx removalmay directly result from processing the waste gas stream in a processorof the invention without additional NOx control technology. In someembodiments, such NOx removal may result from a combination ofprocessing the waste gas stream in a processor of the invention andusing a combustion modification technology. As such, in someembodiments, a pre-combustion modification technology such as combustionstaging or flue gas recirculation (FGR) may be used. Alternatively, NOxemissions may be reduced using a post-combustion modification technologyin combination with processing the waste gas stream in a processor ofthe invention. In such embodiments, a post-combustion modificationtechnology such as selective catalytic reduction (SCR) or selectivenon-catalytic reduction (SNCR) may be used. Combinations ofpre-combustion and post-combustion modification technologies may be usedin combination with processing the waste gas stream in a processor ofthe invention as well.

Aqueous absorption of NOx may be enhanced by forced oxidation of NO toNO₂, which NO₂ is more soluble in solutions of the invention, whichinclude solutions comprising proton-removing agents, divalent cations,or both proton-removing agent and divalent cations. In some embodiments,hydrogen peroxide (H₂O₂) (e.g., hydrogen peroxide in methanol) may beinjected into the waste gas stream to oxidize NO to NO₂ as described inU.S. Pat. No. 5,670,122, which is incorporated herein by reference inits entirety. In some embodiments, the molar ratio of injected H₂O₂(MeOH) to total pollutants is 0.01 to 5.0, such as 0.1 to 4.0, including0.1 to 3.0, for example, 0.1 to 2.0, 0.1 to 1.0, or 0.1 to 0.5. Forexample, if 1 mole of H₂O₂ (MeOH) is injected for 2 moles of totalpollutants, the molar ratio of injected H₂O₂ (MeOH) to total pollutantsis 0.5. Mechanistically, this technique may induce free-radical-mediatedoxidation of NO to NO₂, the formation of which allows for wet-scrubbingin, for example, coal-fired power plants lacking post-modificationtechnology for NOx control (e.g., SCR systems). In some embodiments,chelating agents may be used to improve absorption of NO₂, particularlyincreased concentrations resulting from forced oxidation of NO to NO₂.In some embodiments, nitrates formed from NO₂ absorption may beincorporated into a hydrotalcite (aluminum-magnesiumcarbonate-hydroxide) matrix. In some embodiments, aqueous-basedtransition metal-catalyzed reduction of NOx to N₂, which may be releasedto the atmosphere with N₂ in the cleaned waste gas stream.

As above, metals in the waste gas stream may be in any available form.Using mercury as a non-limiting metal example, elemental mercury (Hg⁰)and/or different forms of gaseous and particulate mercury compounds suchas mercuric oxide (HgO), mercuric chloride (HgCl₂), mercurous chloride(Hg₂Cl₂), particulate mercury (Hg(p)), and the like may be emitted tothe atmosphere from combustion of coal and other mercury-containingfuels. The average concentration of mercury in flue gases resulting fromcoal combustion in the United States may be about 3 ppb while mercuryemissions from waste-to-energy (WtE) or energy-from-waste (EfW) plantsmay range from 0 ppb to 100 ppb. As such, mercury emissions may varygreatly. In some embodiments, the invention provides for at least 5%,10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%,80%, 85%, 90%, 95%, or 99.9% removal of mercury and/or any other tracemetals (e.g., Ag, As, Ba, Be, Cd, Co, Cr, Cu, Mo, Ni, Pb, Sb, Se, Tl, V,Zn, etc.) from a waste gas stream. In some embodiments, for example, theinvention provides for at least 80% removal of mercury and/or any othertrace metals (e.g., Ag, As, Ba, Be, Cd, Co, Cr, Cu, Mo, Ni, Pb, Sb, Se,Tl, V, Zn, etc.) from a waste gas stream. In such embodiments, removalof mercury and/or any other trace metals may directly result fromprocessing the waste gas stream in a processor of the invention withoutadditional control technology (e.g., mercury control technology). Insome embodiments, such trace metal (e.g., mercury) removal may resultfrom a combination of processing the waste gas stream in a processor ofthe invention and using control technology (e.g., mercury controltechnology). Using mercury as a non-limiting metal example, in someembodiments, one or more non-specific mercury control technologies maybe used including the use of electrostatic precipitators, fabricfilters, flue gas desulfurization (FGD), and/or selective catalyticreduction (SCR). For example, in some embodiments, electrostaticprecipitators may be used to remove particulate mercury; fabric filtersmay be used to remove oxidized mercury adsorbed onto fly ash, elementalmercury adsorbed onto fly ash, or particulate mercury; FGD, in additionto removing SOx from flue gas, may be used to remove oxidized mercuryfrom flue gas; and SCR may be used to decrease the amount of elementalmercury in the flue gas; or some combination of the foregoing. In someembodiments, one or more specific mercury control technologies may beused in combination with processing the waste gas stream in a processorof the invention. For example, in some embodiments, sorbent injection(e.g., injection of activated carbon or halogenated carbon) or passageof the waste gas stream through an adsorbent may be used. In anothernon-limiting example, chemical conversion of elemental mercury tonon-volatile mercury compounds (e.g., enhanced FGD using dedicatedoxidation schemes) or may be used. Indeed, multiple oxidation approachesmay be used to convert mercury and/or any other trace metals into asoluble form (e.g., divalent mercury) that can more easily undergoaqueous scrubbing or that can be more easily taken up by an aqueoussolution. As discussed above, the injection of hydrogen peroxide (e.g.,hydrogen peroxide in methanol) would be one such method of oxidation. Inaddition, injection of chlorine in various forms (HCl, Cl₂), indifferent concentration, and/or at different temperatures in thecombustor or waste gas stream may produce metal species (e.g., divalentmercury such as HgCl₂) that are soluble in solutions of the invention,which comprise proton-removing agents and/or divalent cations. In someembodiments, reduction approaches may be used to convert metal speciesinto more soluble or less toxic forms that can undergo aqueousscrubbing. For example, in some embodiments, Cr⁶⁺ from the waste gasstream, industrial waste source of proton-removing agents (e.g., flyash), and/or industrial waste source of divalent cations may be reducedto Cr³⁺, which is a non-toxic relative to hexavalent chromium (Cr⁶⁺).Combinations of non-specific and specific trace metal (e.g., mercury)control technologies may be used in combination with processing thewaste gas stream in a processor of the invention as well.

As described above in reference to CO₂, although a waste gas stream froman industrial plant offers a relatively concentrated source of waste gasstream components such as SOx, NOx, mercury, and the like fromcombustion of fossil fuels, methods and systems of the invention arealso applicable to removing such waste gas stream components from lessconcentrated sources (e.g., atmospheric air), which contain a much lowerconcentration of such components than, for example, flue gas. Thus, insome embodiments, methods and systems encompass decreasing theconcentration of waste gas stream components such as SOx, NOx, mercury,and the like in atmospheric air by producing compositions of theinvention. As with waste gas streams, the concentration of SOx, NOx,mercury, and the like in a portion of atmospheric air may be decreasedby 10% or more, 20% or more, 30% or more, 40% or more, 50% or more, 60%or more, 70% or more, 80% or more, 90% or more, 95% or more, 99% ormore, 99.9% or more, or 99.99%. Such decreases in waste gas streamcomponent such as SOx, NOx, mercury, and the like may be accomplishedwith yields as described herein, or with higher or lower yields, and maybe accomplished in one processing step or in a series of processingsteps.

Source of Proton-Removing Agents or Methods for Effecting Proton Removal

In some embodiments, the invention provides for contacting a volume ofan aqueous solution with a source of carbon dioxide to produce acomposition comprising carbonates, bicarbonates, or carbonates andbicarbonates, wherein the composition is a solution or slurry.Contacting the aqueous solution with the source of carbon dioxidefacilitates dissolution of CO₂ into the aqueous solution producingcarbonic acid, a species in equilibrium with both bicarbonate andcarbonate. In order to produce compositions of the invention (e.g.,precipitation material comprising carbonates, bicarbonates, orcarbonates and bicarbonates), protons are removed from various species(e.g. carbonic acid, bicarbonate, hydronium, etc.) in the aqueoussolution to shift the equilibrium toward bicarbonate, carbonate, orsomewhere in between. As protons are removed, more CO₂ goes intosolution. In some embodiments, proton-removing agents and/or methods areused while contacting an aqueous solution with CO₂ to increase CO₂absorption in one phase of the reaction, wherein the pH may remainconstant, increase, or even decrease, followed by a rapid removal ofprotons (e.g., by addition of a base), which, In some embodiments, maycause rapid precipitation of precipitation material. Protons may beremoved from the various species (e.g. carbonic acid, bicarbonate,hydronium, etc.) by any convenient approach, including, but not limitedto use of naturally occurring proton-removing agents, use ofmicroorganisms and fungi, use of synthetic chemical proton-removingagents, recovery of waste streams from industrial processes, and usingelectrochemical means.

Naturally occurring proton-removing agents encompass any proton-removingagents found in the wider environment that may create or have a basiclocal environment. Some embodiments provide for naturally occurringproton-removing agents including minerals that create basic environmentsupon addition to solution. Such minerals include, but are not limitedto, lime (CaO); periclase (MgO); iron hydroxide minerals (e.g., goethiteand limonite); and volcanic ash. Methods for digestion of such mineralsand rocks comprising such minerals are described in U.S. patentapplication Ser. No. 12/501,217, filed 10 Jul. 2009, which isincorporated herein by reference in its entirety. Some embodimentsprovide for using naturally occurring bodies of water as a sourceproton-removing agents, which bodies of water comprise carbonate,borate, sulfate, or nitrate alkalinity, or some combination thereof. Anyalkaline brine (e.g., surface brine, subsurface brine, a deep brine,etc.) is suitable for use in the invention. In some embodiments, asurface brine comprising carbonate alkalinity provides a source ofproton-removing agents. In some embodiments, a surface brine comprisingborate alkalinity provides a source of proton-removing agents. In someembodiments, a subsurface brine comprising carbonate alkalinity providesa source of proton-removing agents. In some embodiments, a subsurfacebrine comprising borate alkalinity provides a source of proton-removingagents. In some embodiments, a deep brine comprising carbonatealkalinity provides a source of proton-removing agents. In someembodiments, a deep brine comprising borate alkalinity provides a sourceof proton-removing agents. Examples of naturally alkaline bodies ofwater include, but are not limited to surface water sources (e.g.alkaline lakes such as Mono Lake in California) and ground water sources(e.g. basic aquifers such as the deep geologic alkaline aquifers locatedat Searles Lake in California). Other embodiments provide for use ofdeposits from dried alkaline bodies of water such as the crust alongLake Natron in Africa's Great Rift Valley. For additional sources ofbrines and evaporites, see U.S. Provisional Patent Application No.61/264,564, filed 25 Nov. 2009, which is incorporated herein byreference in its entirety. In some embodiments, organisms that excretebasic molecules or solutions in their normal metabolism are used asproton-removing agents. Examples of such organisms are fungi thatproduce alkaline protease (e.g., the deep-sea fungus Aspergillus ustuswith an optimal pH of 9) and bacteria that create alkaline molecules(e.g., cyanobacteria such as Lyngbya sp. from the Atlin wetland inBritish Columbia, which increases pH from a byproduct ofphotosynthesis). In some embodiments, organisms are used to produceproton-removing agents, wherein the organisms (e.g., Bacillus pasteurii,which hydrolyzes urea to ammonia) metabolize a contaminant (e.g. urea)to produce proton-removing agents or solutions comprisingproton-removing agents (e.g., ammonia, ammonium hydroxide). In someembodiments, organisms are cultured separately from the precipitationreaction mixture, wherein proton-removing agents or solution comprisingproton-removing agents are used for addition to the precipitationreaction mixture. In some embodiments, naturally occurring ormanufactured enzymes are used in combination with proton-removing agentsto invoke precipitation of precipitation material. Carbonic anhydrase,which is an enzyme produced by plants and animals, acceleratestransformation of carbonic acid to bicarbonate in aqueous solution. Assuch, carbonic anhydrase may be used to enhance dissolution of CO₂ andaccelerate precipitation of precipitation material, as described infurther detail herein.

Chemical agents for effecting proton removal generally refer tosynthetic chemical agents that are produced in large quantities and arecommercially available. For example, chemical agents for removingprotons include, but are not limited to, hydroxides, organic bases,super bases, oxides, ammonia, and carbonates. Hydroxides includechemical species that provide hydroxide anions in solution, including,for example, sodium hydroxide (NaOH), potassium hydroxide (KOH), calciumhydroxide (Ca(OH)₂), or magnesium hydroxide (Mg(OH)₂). Organic bases arecarbon-containing molecules that are generally nitrogenous basesincluding primary amines such as methyl amine, secondary amines such asdiisopropylamine, tertiary amines such as diisopropylethylamine,aromatic amines such as aniline, heteroaromatics such as pyridine,imidazole, and benzimidazole, and various forms thereof. In someembodiments, an organic base selected from pyridine, methylamine,imidazole, benzimidazole, histidine, and a phosphazene is used to removeprotons from various species (e.g., carbonic acid, bicarbonate,hydronium, etc.) for preparation of compositions of the invention. Insome embodiments, ammonia is used to raise pH to a level sufficient forpreparation of compositions of the invention. Super bases suitable foruse as proton-removing agents include sodium ethoxide, sodium amide(NaNH₂), sodium hydride (NaH), butyl lithium, lithium diisopropylamide,lithium diethylamide, and lithium bis(trimethylsilyl)amide. Oxidesincluding, for example, calcium oxide (CaO), magnesium oxide (MgO),strontium oxide (SrO), beryllium oxide (BeO), and barium oxide (BaO) arealso suitable proton-removing agents that may be used. Carbonates foruse in the invention include, but are not limited to, sodium carbonate.

In addition to comprising cations (e.g., Ca²⁺, Mg²⁺, etc.) and othersuitable metal forms suitable for use in the invention, waste streamsfrom various industrial processes (i.e., industrial waste streams) mayprovide proton-removing agents. Such waste streams include, but are notlimited to, mining wastes; ash (e.g., coal ash such as fly ash, bottomash, boiler slag); slag (e.g. iron slag, phosphorous slag); cement kilnwaste (e.g., cement kiln dust (CKD)); oil refinery/petrochemicalrefinery waste (e.g. oil field and methane seam brines); coal seamwastes (e.g. gas production brines and coal seam brine); paperprocessing waste; water softening waste brine (e.g., ion exchangeeffluent); silicon processing wastes; agricultural waste; metalfinishing waste; high pH textile waste; and caustic sludge. Miningwastes include any wastes from the extraction of metal or anotherprecious or useful mineral from the earth. In some embodiments, wastesfrom mining are used to modify pH, wherein the waste is selected fromred mud from the Bayer aluminum extraction process; waste from magnesiumextraction from seawater (e.g., Mg(OH)₂ such as that found in MossLanding, California); and wastes from mining processes involvingleaching. For example, red mud may be used to modify pH as described inU.S. Provisional Patent Application No. 61/161,369, filed 18 Mar. 2009,which is incorporated herein by reference in its entirety. Red mud,depending on processing conditions and source material (e.g., bauxite)might comprise Fe₂O₃, Al₂O₃, SiO₂, Na₂O, CaO, TiO₂, K₂O, MgO, CO₂, S₂O,MnO₂, P₂O₅, each of which species are loosely listed in order from mostabundant to least abundant, and each of which species are expressed asoxides for convenience. Coal ash, cement kiln dust, and slag,collectively waste sources of metal oxides, further described in U.S.patent application Ser. No. 12/486,692, filed 17 Jun. 2009, thedisclosure of which is incorporated herein in its entirety, may be usedin alone or in combination with other proton-removing agents to provideproton-removing agents for the invention. Agricultural waste, eitherthrough animal waste or excessive fertilizer use, may contain potassiumhydroxide (KOH) or ammonia (NH₃) or both. As such, agricultural wastemay be used in some embodiments of the invention as a proton-removingagent. This agricultural waste is often collected in ponds, but it mayalso percolate down into aquifers, where it can be accessed and used.

Electrochemical methods are another means to remove protons from variousspecies in a solution, either by removing protons from solute (e.g.,deprotonation of carbonic acid or bicarbonate) or from solvent (e.g.,deprotonation of hydronium or water). Deprotonation of solvent mayresult, for example, if proton production from CO₂ dissolution matchesor exceeds electrochemical proton removal from solute molecules. In someembodiments, low-voltage electrochemical methods are used to removeprotons, for example, as CO₂ is dissolved in the precipitation reactionmixture or a precursor solution to the precipitation reaction mixture(i.e., a solution that may or may not contain divalent cations). In someembodiments, CO₂ dissolved in an aqueous solution that does not containdivalent cations is treated by a low-voltage electrochemical method toremove protons from carbonic acid, bicarbonate, hydronium, or anyspecies or combination thereof resulting from the dissolution of CO₂. Alow-voltage electrochemical method operates at an average voltage of 2,1.9, 1.8, 1.7, or 1.6 V or less, such as 1.5, 1.4, 1.3, 1.2, 1.1 V orless, such as 1 V or less, such as 0.9 V or less, 0.8 V or less, 0.7 Vor less, 0.6 V or less, 0.5 V or less, 0.4 V or less, 0.3 V or less, 0.2V or less, or 0.1 V or less. Low-voltage electrochemical methods that donot generate chlorine gas are convenient for use in systems and methodsof the invention. Low-voltage electrochemical methods to remove protonsthat do not generate oxygen gas are also convenient for use in systemsand methods of the invention. In some embodiments, low-voltage methodsdo not generate any gas at the anode. In some embodiments, low-voltageelectrochemical methods generate hydrogen gas at the cathode andtransport it to the anode where the hydrogen gas is converted toprotons. Electrochemical methods that do not generate hydrogen gas mayalso be convenient. In some instances, electrochemical methods to removeprotons do not generate any gaseous by-byproduct. Electrochemicalmethods for effecting proton removal are further described in U.S.patent application Ser. No. 12/344,019, filed 24 Dec. 2008; U.S. patentapplication Ser. No. 12/375,632, filed 23 Dec. 2008; InternationalPatent Application No. PCT/US08/088,242, filed 23 Dec. 2008;International Patent Application No. PCT/US09/32301, filed 28 Jan. 2009;and International Patent Application No. PCT/US09/48511, filed 24 Jun.2009, each of which are incorporated herein by reference in theirentirety.

Alternatively, electrochemical methods may be used to produce causticmolecules (e.g., hydroxide) through, for example, the chlor-alkaliprocess, or modification thereof (e.g., low-voltage modification).Electrodes (i.e., cathodes and anodes) may be present in the apparatuscontaining the aqueous solution or waste gas-charged (e.g., CO₂-charged)solution, and a selective barrier, such as a membrane, may separate theelectrodes. Electrochemical systems and methods for removing protons mayproduce by-products (e.g., hydrogen) that may be harvested and used forother purposes. Additional electrochemical approaches that may be usedin systems and methods of the invention include, but are not limited to,those described in U.S. Provisional Patent Application No. 61/081,299,filed 16 Jul. 2008, and U.S. Provisional Patent Application No.61/091,729, the disclosures of which are incorporated herein byreference. Combinations of the above mentioned sources ofproton-removing agents and methods for effecting proton removal may beemployed.

Source of Divalent Cations

In some embodiments, the invention provides for contacting a volume of aliquid (e.g., an aqueous solution) with a source of carbon dioxide toproduce a composition comprising carbonates, bicarbonates, or carbonatesand bicarbonates, wherein the composition is a solution or slurry. Toproduce precipitation material comprising carbonates, bicarbonates, orcarbonates and bicarbonates, methods of the invention include contactinga volume of a divalent cation-containing aqueous solution with a sourceof CO₂ and subjecting the resultant solution to conditions thatfacilitate precipitation. Divalent cations may come from any of a numberof different sources of divalent cations depending upon availability ata particular location. Such sources include industrial wastes, seawater,brines, hard waters, rocks and minerals (e.g., lime, periclase, materialcomprising metal silicates such as serpentine and olivine), and anyother suitable source.

In some locations, waste streams from various industrial processes(i.e., industrial waste streams) provide for convenient sources ofdivalent cations (as well as proton-removing agents such as metalhydroxides). Such waste streams include, but are not limited to, miningwastes; ash (e.g., coal ash such as fly ash, bottom ash, boiler slag);slag (e.g. iron slag, phosphorous slag); cement kiln waste (e.g., cementkiln dust); oil refinery/petrochemical refinery waste (e.g. oil fieldand methane seam brines); coal seam wastes (e.g. gas production brinesand coal seam brine); paper processing waste; water softening wastebrine (e.g., ion exchange effluent); silicon processing wastes;agricultural waste; metal finishing waste; high pH textile waste; andcaustic sludge. Ash, cement kiln dust, and slag, collectively wastesources of metal oxides, further described in U.S. patent applicationSer. No. 12/486,692, filed 17 Jun. 2009, which is incorporated herein byreference in its entirety, may be used in any combination with materialcomprising metal silicates, further described in U.S. patent applicationSer. No. 12/501,217, filed 10 Jul. 2009, which is also incorporatedherein by reference in its entirety. Any of the divalent cations sourcesdescribed herein may be mixed and matched for the purpose of practicingthe invention. For example, material comprising metal silicates (e.g.,magnesium silicate minerals such as olivine, serpentine, etc.) may becombined with any of the sources of divalent cations described hereinfor the purpose of practicing the invention.

In some locations, a convenient source of divalent cations forpreparation of compositions of the invention (e.g., precipitationmaterial comprising carbonates, bicarbonates, or carbonates andbicarbonates) is water (e.g., an aqueous solution comprising divalentcations such as seawater or brine), which may vary depending upon theparticular location at which the invention is practiced. Suitableaqueous solutions of divalent cations that may be used include solutionscomprising one or more divalent cations (e.g., alkaline earth metalcations such as Ca²⁺ and Mg²⁺). In some embodiments, the aqueous sourceof divalent cations comprises alkaline earth metal cations. In someembodiments, the alkaline earth metal cations include calcium,magnesium, or a mixture thereof. In some embodiments, the aqueoussolution of divalent cations comprises calcium in amounts ranging from50 to 50,000 ppm, 50 to 40,000 ppm, 50 to 20,000 ppm, 100 to 10,000 ppm,200 to 5000 ppm, or 400 to 1000 ppm. In some embodiments, the aqueoussolution of divalent cations comprises magnesium in amounts ranging from50 to 40,000 ppm, 50 to 20,000 ppm, 100 to 10,000 ppm, 200 to 10,000ppm, 500 to 5000 ppm, or 500 to 2500 ppm. In some embodiments, whereCa²⁺ and Mg²⁺ are both present, the ratio of Ca²⁺ to Mg²⁺ (i.e.,Ca²⁺:Mg²⁺) in the aqueous solution of divalent cations is between 1:1and 1:2.5; 1:2.5 and 1:5; 1:5 and 1:10; 1:10 and 1:25; 1:25 and 1:50;1:50 and 1:100; 1:100 and 1:150; 1:150 and 1:200; 1:200 and 1:250; 1:250and 1:500; 1:500 and 1:1000, or a range thereof. For example, in someembodiments, the ratio of Ca²⁺ to Mg²⁺ in the aqueous solution ofdivalent cations is between 1:1 and 1:10; 1:5 and 1:25; 1:10 and 1:50;1:25 and 1:100; 1:50 and 1:500; or 1:100 and 1:1000. In someembodiments, the ratio of Mg²⁺ to Ca²⁺ (i.e., Mg²⁺:Ca²⁺) in the aqueoussolution of divalent cations is between 1:1 and 1:2.5; 1:2.5 and 1:5;1:5 and 1:10; 1:10 and 1:25; 1:25 and 1:50; 1:50 and 1:100; 1:100 and1:150; 1:150 and 1:200; 1:200 and 1:250; 1:250 and 1:500; 1:500 and1:1000, or a range thereof. For example, in some embodiments, the ratioof Mg²⁺ to Ca²⁺ in the aqueous solution of divalent cations is between1:1 and 1:10; 1:5 and 1:25; 1:10 and 1:50; 1:25 and 1:100; 1:50 and1:500; or 1:100 and 1:1000.

The aqueous solution of divalent cations may comprise divalent cationsderived from freshwater, brackish water, seawater, or brine (e.g.,naturally occurring brines or anthropogenic brines such as geothermalplant wastewaters, desalination plant waste waters), as well as otheraqueous solutions having a salinity that is greater than that offreshwater, any of which may be naturally occurring or anthropogenic.For convenience in describing the invention, freshwater may beconsidered to have a salinity of less than 0.5 ppt (parts per thousand).Brackish water may comprise more salt than freshwater, but not as muchas salt as seawater. Brackish water may be considered to have a salinityranging from about 0.5 to about 35 ppt. Seawater may be water from asea, an ocean, or any other body of water that has a salinity rangingfrom about 35 to about 50 ppt. Brine may have a salinity that is about50 ppt or greater. As such, brine may be water saturated or nearlysaturated with salt. In some embodiments, the water source from whichdivalent cations are derived is a mineral rich (e.g., calcium-richand/or magnesium-rich) freshwater source. In some embodiments, the watersource from which divalent cations are derived is a naturally occurringsaltwater source selected from a sea, an ocean, a lake, a swamp, anestuary, a lagoon, a surface brine, a deep brine, an alkaline lake, aninland sea, or the like. In some embodiments, the water source fromwhich divalent cations are derived is a surface brine. In someembodiments, the water source from which divalent cations are derived isa subsurface brine. In some embodiments, the water source from whichdivalent cations are derived is a deep brine. In some embodiments, thewater source from which divalent cations are derived is aCa—Mg—Na—(K)—Cl; Na—(Ca)—SO₄—Cl; Mg—Na—(Ca)—SO₄—Cl; Na—CO₃—Cl; orNa—CO₃—SO₄—Cl brine. In some embodiments, the water source from whichdivalent cation are derived is an anthropogenic brine selected from ageothermal plant wastewater or a desalination wastewater.

Freshwater is often a convenient source of divalent cations (e.g.,cations of alkaline earth metals such as Ca²⁺ and Mg²⁺). Any of a numberof suitable freshwater sources may be used, including freshwater sourcesranging from sources relatively free of minerals to sources relativelyrich in minerals. Mineral-rich freshwater sources may be naturallyoccurring, including any of a number of hard water sources, lakes, orinland seas. Some mineral-rich freshwater sources such as alkaline lakesor inland seas (e.g., Lake Van in Turkey) also provide a source ofpH-modifying agents. Mineral-rich freshwater sources may also beanthropogenic. For example, a mineral-poor (soft) water may be contactedwith a source of divalent cations such as alkaline earth metal cations(e.g., Ca²⁺, Mg²⁺, etc.) to produce a mineral-rich water that issuitable for methods and systems described herein. Divalent cations orprecursors thereof (e.g. salts, minerals) may be added to freshwater (orany other type of water described herein) using any convenient protocol(e.g., addition of solids, suspensions, or solutions). In someembodiments, divalent cations selected from Ca²⁺ and Mg²⁺ are added tofreshwater. In some embodiments, monovalent cations selected from Na⁺and K⁺ are added to freshwater. In some embodiments, freshwatercomprising Ca²⁺ is combined with material comprising metal silicates,ash (e.g., fly ash, bottom ash, boiler slag), or products or processedforms thereof, including combinations of the foregoing, yielding asolution comprising calcium and magnesium cations.

In some embodiments, an aqueous solution of divalent cations may beobtained from an industrial plant that is also providing a waste gasstream (e.g., combustion gas stream). For example, in water-cooledindustrial plants, such as seawater-cooled industrial plants, water thathas been used by an industrial plant for cooling may then be used aswater for producing precipitation material. If desired, the water may becooled prior to entering a precipitation system of the invention. Suchapproaches may be employed, for example, with once-through coolingsystems. For example, a city or agricultural water supply may beemployed as a once-through cooling system for an industrial plant. Waterfrom the industrial plant may then be employed for producingprecipitation material, wherein output water has a reduced hardness andgreater purity.

The aqueous solution of divalent cations may further provideproton-removing agents, which may be expressed as alkalinity or theability of the divalent cation-containing solution to neutralize acidsto the equivalence point of carbonate or bicarbonate. Alkalinity (A_(T))may be expressed by the following equation

A_(T)=[HCO₃ ⁻]_(T)+2[CO₃ ²⁺]_(T)+[B(OH)₄ ⁻]_(T)+[OH⁻]_(T)+2[PO₄³⁻]_(T)+[HPO₄ ²⁻]_(T)+[SiO(OH)₃ ⁻]_(T)−[H⁺]_(sws)−[HSO₄ ⁻],

wherein “T” indicates the total concentration of the species in thesolution as measured. Other species, depending on the source, maycontribute to alkalinity as well. The total concentration of the speciesin solution is in opposition to the free concentration, which takes intoaccount the significant amount of ion pair interactions that occur, forexample, in seawater. In accordance with the equation, the aqueoussource of divalent cations may have various concentrations ofbicarbonate, carbonate, borate, hydroxide, phosphate, biphosphate,and/or silicate, which may contribute to the alkalinity of the aqueoussource of divalent cations. Any type of alkalinity is suitable for theinvention. For example, in some embodiments, a source of divalentcations high in borate alkalinity is suitable for the invention. In suchembodiments, the concentration borate may exceed the concentration ofany other species in solution including, for example, carbonate and/orbicarbonate In some embodiments, the source of divalent cations has atleast 10, 100, 500, 1000, 1500, 3000, 5000, or more than 5000 mEq ofalkalinity. For example, in some embodiments, the source of divalentcations has between 500 to 1000 mEq of alkalinity.

Like waste gas streams (e.g., various sources of CO₂ described herein),liquid and solid wastes (including multiphasic forms such as slurries ofwaste) such as industrial waste sources of proton-removing agents ordivalent cations are also of concern because of their potentialpolluting effects. Many liquid and solid wastes from industrial sourcescomprise acids, bases, or other constituents that are not suitable fordischarge into the environment due to their polluting effects. In someinstances, the industrial waste may be too acidic. In some instances,the industrial waste may be too alkaline. In yet other instances, theindustrial waste may contain an unacceptable level of heavy metals(e.g., lead, mercury, chromium, etc.) For example, in the Bayer process,an industrial process in which sodium hydroxide is used to selectivelydissolve Al₂O₃, a waste comprising iron, titanium, sodium, silica, andother impurities is generated. This waste, known as red mud, is highlycaustic (pH often in excess of pH 13.2) from residual sodium hydroxide,and its disposal is an on-going environmental concern. Similarly, incoal-fired power plants, ash such as fly ash or bottom ash is generatedin combusting coal. Depending upon the source and makeup of the coalbeing burned, the constituents of the ash may vary considerably and mayinclude substantial amounts of silicon dioxide; calcium oxide; metalsincluding arsenic, beryllium, boron, cadmium, chromium, cobalt, lead,manganese, mercury, molybdenum, selenium, strontium, thallium, andvanadium; and organics such as hydrocarbons, dioxins, and polyaromatichydrocarbons (PAHs). Although ash (e.g., fly ash) can be contained intailings ponds or in landfills, its disposal is also an on-goingenvironmental concern. Similar problems and concerns are encounteredwith other industrial wastes (e.g. wood pulp and paper making wastes,metallurgical wastes, and the like).

In some embodiments, the invention provides a method of neutralizing anindustrial waste stream comprising contacting a first waste stream witha second waste stream to neutralize at least one of the waste streams,which neutralized stream is effectively safe to release into theenvironment (i.e., the neutralized waste stream comprises acceptablelevels of environmental contaminants) In some embodiments, the firstwaste stream is a waste gas stream comprising carbon dioxide. In someembodiments, the first waste stream is a waste gas stream comprisingcarbon dioxide and one or more additional components (e.g., SOx, NOx, Hgand/or other trace metals) in addition to carbon dioxide. In someembodiments, the second waste stream is a liquid, solid, or amultiphasic form thereof. In some embodiments, the first waste stream isa waste gas stream comprising carbon dioxide and the second waste streamis a liquid, solid, or multiphasic form thereof. In some embodiments,the first waste stream is a waste gas stream comprising carbon dioxideand one or more additional components (e.g., SOx, NOx, Hg and/or othertrace metals) in addition to carbon dioxide and the second waste streamis a liquid, solid, or a multiphasic form thereof. In some embodiments,the invention provides a method of neutralizing multiple industrialwaste streams such as two, three, four, five, or more than fiveindustrial waste streams, wherein at least one waste stream comprises awaste gas stream comprising carbon dioxide, and wherein at least onewaste stream is neutralized. In some embodiments of the invention, two,three, four, five, or more than five waste streams are neutralized.Indeed, the invention provides for neutralization of any of the sources(e.g., industrial sources) of proton-removing agents, divalent cations,or combinations thereof that are described herein such that theneutralized source may safely be release into the environment. Forexample, in some embodiments, neutralization methods of the inventioncomprise contacting a first waste stream with a second waste stream,wherein the first waste stream is a waste gas stream comprising carbondioxide and one or more additional components (e.g., SOx, NOx, Hg and/orother trace metals) in addition to carbon dioxide and the second wastestream is red mud, fly ash, or a combination thereof. Each of thesystems described herein may be adapted for neutralization of two ormore waste streams, wherein at least one waste stream comprises a wastegas stream comprising carbon dioxide.

Systems of the invention such as system (200A) of FIG. 2A, which isillustrative and in no way limits the following description to FIG. 2A,may comprise a processor (210) (e.g., reactor) adapted for contacting awaste gas stream (230) comprising CO₂ with an aqueous solutioncomprising divalent cations (250) to cause removal of combustion gasesand particulate matter from the waste gas stream and to formprecipitation material with the divalent cations in the solution.Causing removal of combustion gases (e.g., CO2, SOx, NOx, etc.) andparticulate matter (e.g., metals, fly ash, etc.) from the waste gasstream, as with other embodiments of the invention described herein, iseffected by carbon dioxide and the one or more other components exitingthe waste gas stream and entering the liquid (e.g., the aqueoussolution). As above, waste streams of interest include industrial plantexhaust gas (e.g., a flue gas), which may be obtained from the productsof combustion from burning a fossil or biomass fuel that are thendirected to the smokestack, also known as the flue of an industrialplant. In addition to CO₂ generated by the burning of fuels, CO₂ canalso be released as a result of other industrial processing (e.g.,calcination of minerals in a cement plant). The composition of the fluegas may vary. In certain embodiments, the amount of CO₂ in the flue gasmay range from 350 ppm to 400,000 ppm, such as 2000 ppm to 200,000 ppmand including 2000 ppm to 180,000 ppm. Other components as disclosedherein may also be present in the flue gas, e.g., water, NOx, SOx,mercury and particulate matter. The temperature of the flue gas mayvary, e.g., from 0° C. to 2000° C., such as from 60° C. to 7000° C. andincluding 100° C. to 400° C.

The waste gas stream employed in methods of the invention may beprovided from the industrial plant to the site of precipitation in anyconvenient manner that conveys the waste gas stream from the industrialplant to the precipitation plant. In certain embodiments, the wastestream is provided with a gas conveyor, e.g., a duct, which runs from asite of the industrial plant, e.g., a flue of the industrial plant, toone or more locations of the precipitation site. The source of the wastegas stream may be a distal location relative to the site ofprecipitation, such that the source of the waste gas stream is alocation that is 1 mile or more, such as 10 miles or more, including 100miles or more, from the precipitation location. For example, the wastegas stream may have been transported to the site of precipitation from aremote industrial plant via a CO₂ gas conveyance system, e.g., apipeline. The industrial plant generated CO₂ containing gas may or maynot be processed, e.g., remove other components, etc., before it reachesthe precipitation site (i.e., a carbonate compound precipitation plant).In yet other instances, source of the waste gas stream is proximal tothe precipitation site, where such instances may include instances wherethe precipitation site is integrated with the source of the waste gasstream, such as a power plant that integrates a carbonate compoundprecipitation system.

As indicated above, the waste gas stream may be one that is obtainedfrom a flue or analogous structure of an industrial plant. In theseembodiments, a line, e.g., duct, is connected to the flue so that gasleaves the flue through the line and is conveyed to the appropriatelocation(s) of a precipitation system (described in greater detailbelow). Depending on the particular configuration of the portion of theprecipitation system at which the waste gas stream is employed, thelocation of the source from which the waste gas stream is obtained mayvary, e.g., to provide a waste stream that has the appropriate ordesired temperature. As such, in certain embodiments where a waste gasstream having a temperature ranging for 0° C. to 1800° C., such as 60°C. to 700° C. is desired, the flue gas may be obtained at the exit pointof the boiler or gas turbine, the kiln, or at any point through thepower plant or stack, that provides the desired temperature. Wheredesired, the flue gas is maintained at a temperature above the dewpoint, e.g., 125° C., in order to avoid condensation and relatedcomplications. Where such is not possible, steps may be taken to reducethe adverse impact of condensation, e.g., employing ducting that isstainless steel, fluorocarbon (such as poly(tetrafluoroethylene)) lined,diluted with water and pH controlled, etc., so the duct does not rapidlydeteriorate.

As is in FIG. 2A, which is illustrative and in no way limits thefollowing description to FIG. 2A, system 200A includes a source ofproton-removing agents (240) (e.g., hydroxide ions) for adjusting the pHof the solution to promote the absorption of the combustion gases in thesolution and reaction of the components in the waste gas stream with thedivalent cations in the solution. In various embodiments, the processor(210) (e.g., reactor) is configured for interaction of the waste gasstream (230) with the solution to form a slurry comprising particulatematter from the waste gas stream and precipitation material formed fromthe gases interacting with divalent cations in the solution. In variousembodiments, the processor (210) is operably connected to a treatmentsystem (220) comprising a liquid-solid separator (222) configured toseparate slurry from the processor into a wet cake of precipitationmaterial and a supernatant. In various embodiments, the supernatant,depleted of divalent cations, hydroxide ions, and precipitationmaterial, may be used as feed water for desalination as described inU.S. patent application Ser. No. 12/163,205, filed 27 Jun. 2008, whichis incorporated herein by reference in it entirety. In otherembodiments, the carbon-dioxide processing system may be configured suchthat a portion of the supernatant may be replenished with divalentcations (e.g., alkaline earth metal ions) and proton-removing agents(e.g., hydroxide ions) and re-circulated to the processor (210) (e.g.,reactor). Optionally, as illustrated in FIG. 2A, systems of theinvention may comprise a washer (226) configured to wash wet cake fromthe liquid-solid separator (222) with clean water to remove solublesalts from the wet cake and to produce a washed wet cake (e.g.,desalinated wet cake) of precipitation material (along with spent washwater). System 200A may further comprise a dryer (224) configured to drywet cake to form a raw, dried product, which, in turn, may be refined ina refinery (228) to produce a refined product. Raw, dried product orrefined product may be used to prepare building materials of theinvention depending upon the specification of the building material.

As shown in FIG. 2A, which is illustrative and in no way limits thefollowing description to FIG. 2A, equipment that may be used to removethe gas components (e.g., CO₂, SOx, NOx, etc.) and produce a driedproduct from the precipitation material are commercially available butmay need customization for the system. The processor (210) (e.g.,reactor) may include any of a number of different components, such astemperature control components (e.g., configured to heat the aqueoussolution to a desired temperature), chemical additive components (e.g.,for introducing chemical pH-modifying agents such as KOH, NaOH, etc.),electrolysis components (e.g., cathodes/anodes, etc.), gas-chargingcomponents, pressurization components (e.g., for operating underpressurized conditions such as from 50-800 psi, 100-800 psi, 400-800psi, or any other suitable pressure range), mechanical agitation andphysical stirring components, and components to re-circulate industrialplant flue gas through the precipitation system. The processor 210(e.g., reactor) may contain components that allow for the monitoring ofone or more parameters such as internal reactor pressure, pH,precipitation material particle size, metal-ion concentration,conductivity and alkalinity of the aqueous solution, and partialpressure of the gases. Monitoring conditions during the precipitationprocess can allow for corrective adjustments to be made duringprocessing, or if desired, to increase or decrease production ofprecipitation material.

Also as shown in FIG. 2A, which is illustrative and in no way limits thefollowing description to FIG. 2A, systems of the invention, in variousembodiments, comprise a system for supplying proton-removing agents 240(e.g., hydroxide ions) to cause formation of precipitation material inthe processor (210) (e.g., reactor). Although any convenient source ofproton-removing agents (e.g., hydroxide from commercially availablesodium hydroxide) may be used, in one embodiment, the system includes anelectrochemical system for supplying proton-removing agents (e.g.,hydroxide) to the aqueous cation solution or effecting proton removalfrom the aqueous solution as is illustrated in FIG. 3, and as describedin commonly assigned International Patent Application No.PCT/US08/088,242, filed 23 Dec. 2008, which is incorporated herein byreference in its entirety.

With reference to FIG. 3, the electrochemical system (300) in oneembodiment comprises anode 308 contacting first electrolyte 304; anionexchange membrane 302 separating the first electrolyte from a thirdelectrolyte (330); second electrolyte contacting cathode 310, and cationexchange membrane 324 separating the second electrolyte from the thirdelectrolyte. The ion exchange membranes are positioned in the system toprevent mixing of the first and second electrolytes. A current/voltageregulator (312) may be adapted to increase or decrease the current orvoltage across the cathode and anode in the system as desired. Onapplying a voltage across the anode and cathode, proton-removing agents(e.g., hydroxide) form in the solution in contact with the cathodewithout a gas (e.g., oxygen or chlorine) forming at the anode. As withthe system illustrated in FIG. 2A, which is illustrative and in no waylimits the following description to FIG. 2A, the system of FIG. 3 may beadapted for batch, semi-batch, or continuous operation for supplyingproton-removing agents (e.g., hydroxide) to systems of the inventionsuch as that of FIG. 2A.

To provide for efficiencies, the industrial plant that generates thewaste gas stream may be co-located with the precipitation system. By“co-located” is meant that the distances between the industrial plantand precipitation system range from 10 to 500 yards, such as 25 to 400yards, including 30 to 350 yards. Where desired, the precipitation andindustrial plants may be configured relative to each other to minimizetemperature loss and avoid condensation, as well as minimize ductingcosts, e.g., where the precipitation plant is located within 40 yards ofthe industrial plant.

Also of interest in certain embodiments is a fully integrated plant thatincludes an industrial function (such as power generation, cementproduction, etc.) and a precipitation system of the invention. In suchintegrated plants, conventional industrial plants and precipitationsystem, such as described below, are modified to provide for the desiredintegrated plant. Modifications include, but are not limited to:coordination of stacks, pumping, controls, instrumentation, monitoring,use of plant energy, e.g., steam turbine energy to run portions of theprecipitation component, e.g., mechanical press, pumps, compressors, useof heat from cement and/or power plant obtained from steam or heat fromair to air heat exchanger and the like.

With reference to FIG. 2A, which is illustrative and in no way limitsthe following description to FIG. 2A, the waste gas stream (230)comprising combustion gas (e.g., CO₂) is contacted with the divalentcation aqueous solution (250), which may be delivered to processor 210(e.g., reactor) via a pipeline or in some other convenient manner. Suchcontact may produce a combustion gas-charged aqueous solution, whereincombustion gas molecules (e.g., CO₂, HCl, NOx, SOx, etc.) have combinedwith water molecules to produce new chemical species (e.g., carbonicacid, bicarbonate, carbonate, hydrochloric acid, nitric acid, sulfuricacid, etc.), or where the combustion gas molecules have merely dissolvedin the water. A combustion gas-charged aqueous solution may alsocomprise particulate matter from the combustion gas suspended in theaqueous solution. In various embodiments, as described above, combustiongas may comprise carbon dioxide; carbon monoxide; nitrogen oxides (NOx);sulfur oxides (SOx); sulfides; halides such as hydrogen chloride andhydrogen fluoride, which may also be considered acid gases along with,for example, SOx (e.g., SO₃, SO₂); particulate matter such as fly ash;metals including, but not limited to, arsenic, beryllium, boron,cadmium, chromium, cobalt, lead, manganese, mercury, molybdenum,selenium, strontium, thallium, and vanadium; organics such ashydrocarbons, dioxins, and polynuclear aromatic hydrocarbons (PAH); andradioactive materials. In various embodiments, the system (200A) may beadapted for processing a waste gas stream 230 comprising CO₂ (e.g.,combustion gas) comprising all, or one, or more than one of thesecomponents simultaneously.

Charging the divalent cation-containing aqueous solution with combustiongas in the processor (210) (e.g., reactor) results in an increase in thecombustion gas content in the aqueous solution (e.g., in the form ofcarbonic acid, bicarbonate and carbonate ion) and a decrease inconcentration of combustion gas content in the gas that exits theprocessor (e.g., reactor). In various embodiments, the combustiongas-charged aqueous solution may be acidic, having a pH of 6 or less,such as 5 or less, and including 4 or less. In certain embodiments, theconcentration of CO₂, NOx, SOx, or a combination thereof of the gas thatis used to charge the water is 0.1%, 1%, 5%, 10% or higher, 25% orhigher, including 50% or higher, such as 75%, or even higher. Contactprotocols of interest include, but are not limited to, direct contactingprotocols (e.g., bubbling the gas through the volume of the aqueoussolution), concurrent contacting and mixing (e.g., contact betweenunidirectional flowing gaseous and liquid phase streams), countercurrentmeans (e.g., contact between oppositely flowing gaseous and liquid phasestreams), and the like. Thus, contact may be accomplished through use ofinfusers, bubblers, fluidic Venturi reactors, spargers, gas filters,sprays, trays, flat streams, or packed column reactors, and the like, asmay be convenient and as described in U.S. Pat. No. 7,379,487; U.S.Provisional Patent Application No. 61/158,992, filed 10 Mar. 2009; U.S.Provisional Patent Application No. 61/228,210, filed 24 Jul. 2009; U.S.Provisional Patent Application No. 61/178,360, filed 14 May 2009; U.S.Provisional Patent Application No. 61/221,457, filed 29 Jun. 2009; U.S.Provisional Patent Application No. 61/221,631, filed 30 Jun. 2009; U.S.Provisional Patent Application No. 61/223,657, filed 7 Jul. 2009; U.S.Provisional Patent Application No. 61/289,657, filed 23 Dec. 2009, eachof which is incorporated herein by reference in its entirety. In variousembodiments, the waste gas stream (e.g. combustion gas) may be processedbefore being used to charge the aqueous solution. For example, as,desired, the waste gas stream may be subjected to oxidation conditions(e.g., to convert CO to CO₂, NO to NO₂, and SO₂ to SO₃), as describedfor example in U.S. Pat. No. 5,670,122, which is incorporated herein byreference in its entirety.

Amorphous or crystalline precipitation material comprising carbonates,bicarbonates, or carbonates and bicarbonates, which may further comprisesulfates, sulfites, and/or the like, may be precipitated in processor(210) (e.g., reactor). Precipitation conditions include those thatchange the chemical and/or physical environment of the aqueous solutionto produce the desired precipitation material. For example, thetemperature of the water may be raised to an amount suitable forprecipitation of a desired carbonate or sulfate compound to occur. Insuch embodiments, the temperature of the water may be raised to atemperature from 5 to 70° C., such as from 20 to 50° C., and includingfrom 25 to 45° C. As such, while a given set of precipitation conditionsmay have a temperature ranging from 0 to 100° C., the temperature may beraised in certain embodiments to produce the desired precipitationmaterial. In certain embodiments, the temperature may be raised usingenergy generated from low or zero carbon dioxide emission sources (e.g.,solar energy, wind energy, hydroelectric energy, etc.).

While the pH of the aqueous solution may range from pH 5 to pH 14 (e.g.,pH 7 to pH 14) during a given precipitation process, in certainembodiments the pH may be raised to alkaline levels in order to drivethe precipitation of carbonate and/or sulfur-based (e.g., SO₄, SO₃,etc.) compounds as well as other compounds (e.g., hydroxide compoundsand metal complexes) and particulate matter as desired. In certain ofthese embodiments, the pH is raised to a level that minimizes if noteliminates NOx, SOx, and/or CO₂ gas generation from the processor (e.g.,reactor) during precipitation. Such pH levels cause dissolved gases, inthe form of, for example, carbonates, bicarbonates, sulfates, sulfites,and the like, to be trapped in the precipitation material. In theseembodiments, the pH may be raised to pH 9 or higher, such as pH 10 orhigher, including pH 11 or higher. Where desired, the pH of the water israised using any convenient approach including the use of theelectrochemical system of FIG. 3 as described herein. In certainembodiments, a proton-removing agent (e.g., pH-modifying agent) may beemployed, where examples of such proton-removing agents include oxides,hydroxides (e.g., sodium hydroxide, potassium hydroxide, Mg(OH)₂),carbonates (e.g. sodium carbonate), and the like. The amount ofproton-removing agent (e.g., pH-modifying agent) that is added to thedivalent cation-cation containing aqueous solution may depend on theparticular nature of the proton-removing agent and the volume of theaqueous solution being modified, and may be sufficient to raise the pHof the divalent cation-cation containing aqueous solution to the desiredvalue.

Charging the aqueous solution with combustion gas and precipitation ofprecipitation material (e.g., carbonates, sulfates, sulfites, and/or thelike) may occur in a continuous process or in separate process steps. Assuch, charging and precipitation may occur in the same processor (e.g.,reactor) as shown in FIG. 2A, which is illustrative and in no way limitsthe invention to FIG. 2A. In other embodiments, these two (or more)steps may occur in separate processors or separate units within aprocessor (e.g., gas-liquid contactor, gas-liquid-solid contactor,reactor, etc.). In such embodiments, for example, the aqueous solutionmay first be charged in a gas-liquid or gas-liquid-solid contactor andthe resultant combustion gas-charged aqueous solution may then subjectedto precipitation conditions in a separate reactor. Similarly, it will beappreciated that one or more components of the waste gas stream may beremoved from the waste gas stream through physical trapping in theprecipitation material, or through a combination of physical trappingand precipitation. Thus, for example, mercury or other heavy metals,particulate matter, organics, and/or other components may be trapped inthe precipitation material that renders them stable under desiredconditions.

With reference to FIG. 2A, which is illustrative and in no way limitsthe following description to FIG. 2A, a storage stable product may beprecipitated in processor 210, which may occur in a sub-system thereof,including, but not limited to a gas-liquid contactor, a gas-liquid-solidcontactor, a reactor, or in any combination of the foregoing. As above,precipitation conditions of interest include those that modulate thechemical and/or physical environment of the aqueous solution to producethe desired precipitation material. For example, the temperature of theaqueous solution may be raised to an amount suitable for precipitationof a desired carbonate or sulfate compound to occur. In certainembodiments, excess and/or process heat from the industrial plantcarried in the waste gas stream may be employed to raise the temperatureof the aqueous solution during precipitation either as hot gases orsteam. In certain embodiments, contact of the water with the waste gasstream may have raised the aqueous solution to the desired temperature,where in other embodiments, the aqueous solution may need to be cooledto the desired temperature.

In various embodiments, ash is employed as a pH-modifying agent, e.g.,to increase the pH of the combustion gas-charged aqueous solution. Ashmay be used as the sole pH modifier or in conjunction with one or moreadditional pH modifiers. Of interest in certain embodiments is use of acoal ash as the ash, which coal ash may be the residue produced in powerplant boilers or coal burning furnaces, for example, chain grateboilers, cyclone boilers, and fluidized bed boilers, from burningpulverized anthracite, lignite, bituminous, or sub-bituminous coal. Suchcoal ash includes fly ash, which is the finely divided coal ash carriedfrom the furnace by exhaust or flue gases, and bottom ash which collectsat the base of the furnace as agglomerates.

Fly ashes are generally highly heterogeneous, and include of a mixtureof glassy particles with various identifiable crystalline phases such asquartz, mullite, and various iron oxides. Fly ashes of interest includeType F and Type C fly ash. The Type F and Type C fly ashes referred toabove are defined by CSA Standard A23.5 and ASTM C618. The chiefdifference between these classes is the amount of calcium, silica,alumina, and iron content in the coal ash. The chemical properties ofthe fly ash are largely influenced by the chemical content of the coalburned (i.e., anthracite, bituminous, and lignite). Fly ashes ofinterest include substantial amounts of silica (silicon dioxide, SiO₂)(both amorphous and crystalline) and lime (calcium oxide, CaO, magnesiumoxide, MgO).

Table 1 below provides the chemical makeup of various types of fly ashthat find use in embodiments of the invention.

TABLE 1 Chemical makeup of various types of fly ash. ComponentBituminous Sub-bituminous Lignite SiO₂ (%) 20-60 40-60 15-45 Al₂O₃ (%) 5-35 20-30 20-25 Fe₂O₃ (%) 10-40  4-10  4-15 CaO (%)  1-12  5-30 15-40

The burning of harder, older anthracite and bituminous coal typicallyproduces Class F fly ash. Class F fly ash is pozzolanic in nature, andcontains less than 10% lime (CaO). Fly ash produced from the burning ofyounger lignite or sub bituminous coal, in addition to having pozzolanicproperties, also has some self-cementing properties. In the presence ofwater, Class C fly ash will harden and gain strength over time. Class Cfly ash generally contains more than 20% lime (CaO). Alkali and sulfate(SO₄) contents are generally higher in Class C fly ashes.

Fly ash material solidifies while suspended in exhaust gases and iscollected using various approaches, for example, by electrostaticprecipitators or filter bags. Since the particles solidify whilesuspended in the exhaust gases, fly ash particles are generallyspherical in shape and range in size from 0.5 μm to 100 μm. Fly ashes ofinterest include those in which at least about 80%, by weight comprisesparticles of less than 45 microns. Also of interest in certainembodiments of the invention is the use of highly alkaline fluidized bedcombustor (FBC) fly ash.

Also of interest in various embodiments is the use of bottom ash. Bottomash is formed as agglomerates in coal combustion boilers from thecombustion of coal. Such combustion boilers may be wet bottom boilers ordry bottom boilers. When produced in a wet or dry bottom boiler, thebottom ash is quenched in water. The quenching results in agglomerateshaving a size in which 90% fall within the particle size range of 0.1 mmto 20 mm, where the bottom ash agglomerates have a wide distribution ofagglomerate size within this range. The main chemical components of abottom ash are silica and alumina with lesser amounts of oxides of Fe,Ca, Mg, Mn, Na, and K, as well as sulfur and carbon.

Also of interest in certain embodiments is the use of volcanic ash asthe ash. Volcanic ash is made up of small tephra (i.e., bits ofpulverized rock and glass created by volcanic eruptions) less than 2millimeters (0.079 in) in diameter.

In various embodiments, cement kiln dust (CKD) may be added to thecomposition-producing reaction mixture as a means of modifying pH. Thenature of the fuel and the means of combusting the fuel for calciningmay influence the chemical composition of the CKD, which may contain ashfrom the fuel. Thus, ash and/or CKD may be used as a portion of themeans for modifying pH, or the sole means, and a variety of othercomponents may be utilized with specific ashes and/or CKDs, based onchemical composition of the ash and/or CKD.

In some embodiments, ash is added to the aqueous solution (e.g.,precipitation reaction mixture) as one source of these additionalreactants, to produce precipitation material, which may contain one ormore components such as amorphous silica, crystalline silica, calciumsilicates, calcium alumina silicates, or any other moiety which mayresult from the reaction of ash in the process for producingcompositions of the invention.

The ash employed in various embodiments may be contacted with theaqueous solution to achieve a desired pH using any convenient protocol,including, for example, placing an amount of ash into the processor(e.g., reactor) holding the aqueous solution, where the amount of ashadded is sufficient to raise the pH to the desired level; flowing theaqueous solution through an amount of the ash, in the form of a columnor bed; etc.

In certain embodiments where the pH is not raised to a level of pH 12 orhigher, the fly ash employed may not dissolve but instead may remain asa particulate composition. Undissolved fly ash may be separated (e.g.,filtered) from the remainder of the reaction product (e.g.,precipitation material) for a subsequent use. Alternatively, the aqueoussolution may be flowed through an amount of fly ash that is provided inan immobilized configuration (e.g., in a column or analogous structure),which provides for flow through of an aqueous solution through the flyash but does not allow fly ash to flow out of the structure with theaqueous solution. This embodiment does not require separation ofundissolved fly ash from the product solution. In yet other embodimentswhere the pH exceeds 12, the fly ash may dissolve and provide forpozzolanic products as described in greater detail below.

In embodiments where fly ash is utilized in the producing compositionsof the invention, the fly ash may first be removed from the flue gas bymeans such as electrostatic precipitation, or may be utilized directlyvia the flue gas. The use of fly ash in some embodiments of theinvention may provide reactants such as alumina or silica in addition toraising the pH.

In certain embodiments, slag is employed as a pH-modifying agent, forexample, to increase the pH of the combustion gas-charged water. Theslag may be used as a as the sole pH modifier or in conjunction with oneor more additional pH modifiers (e.g., ashes, etc.). Slag, which isgenerated from the processing of metals, may contain calcium andmagnesium oxides as well as iron, silicon and aluminum compounds. Incertain embodiments, the use of slag as a pH-modifying material mayprovide additional benefits via the introduction of reactive silica andalumina to the precipitation material. Slags of interest include, butare not limited to, blast furnace slag from iron smelting, slag fromelectric-arc or blast furnace processing of steel, copper slag, nickelslag, and phosphorus slag.

As indicated above, ash (or slag in certain embodiments) may be employedin certain embodiments as the sole way to modify the pH of the aqueoussolution to the desired level. In yet other embodiments, one or moreadditional pH-modifying agents or methods may be employed in conjunctionwith the use of ash.

Where desired, additives other than pH-modifying agents may also beintroduced into the aqueous solution in order to influence the nature ofthe precipitation material that is produced. As such, certainembodiments of the methods include providing an additive in the aqueoussolution before or during the time when the aqueous solution issubjected to the precipitation conditions. Certain calcium carbonatepolymorphs may be favored by trace amounts of certain additives. Forexample, vaterite, a highly unstable polymorph of CaCO₃ thatprecipitates in a variety of different morphologies and converts rapidlyto calcite, may be obtained at very high yields by including traceamounts of lanthanum as lanthanum chloride in a supersaturated solutionof calcium carbonate. Other additives besides lanthanum that are ofinterest include, but are not limited to, transition metals and thelike. For instance, the addition of ferrous or ferric iron is known tofavor the formation of disordered dolomite (protodolomite) where itwould not form otherwise.

Accordingly, a set of precipitation conditions to produce a desiredprecipitation material from a divalent cation-containing aqueoussolution includes, in certain embodiments, reaction temperature and pH,and, in some instances, the concentrations of additives and ionicspecies in the aqueous solution. Precipitation conditions may alsoinclude factors such as mixing rate, forms of agitation such asultrasonics, and the presence of seed crystals, catalysts, membranes, orsubstrates. In some embodiments, precipitation conditions includesupersaturated conditions, temperature, pH, and/or concentrationgradients, or cycling or changing any of these parameters. The protocolsemployed to prepare precipitation material according to the inventionmay be batch or continuous protocols. It will be appreciated thatprecipitation conditions may be different to produce a givenprecipitation material in a continuous flow system compared to a batchsystem.

In certain embodiments, contact between the divalent cation-containingaqueous solution and the combustion gas may be accomplished using anyconvenient protocol (e.g., spray gun, segmented flow-tube reactor) tocontrol the range of sizes of precipitation material particles. One ormore additives may be added to the source of divalent cations to controlthe range of sizes of precipitation material, including, but not limitedto, flocculants, dispersants, surfactants, anti-scalants, crystal growthretarders, sequestration agents, etc.

Contact of the divalent cation-containing aqueous solution with thewaste gas stream (e.g., combustion gas) may occur before, during, and/orafter the time when the aqueous solution is subjected to precipitationconditions. Accordingly, embodiments of the invention include methods inwhich the aqueous solution is contacted with the waste gas stream priorto subjecting the solution to mineral precipitation conditions.Embodiments of the invention also include methods in which the aqueoussolution is contacted with the waste gas stream while the aqueoussolution is being subjected to precipitation conditions. Embodiments ofthe invention include methods in which the aqueous solution is contactedwith the waste gas stream both prior to subjecting the aqueous solutionto precipitation conditions and while the aqueous solution is beingsubjected to precipitation conditions. In some embodiments, the sameaqueous solution may be cycled more than once, wherein a first cycle ofprecipitation removes, for example, carbonates (e.g., calcium carbonate,magnesium carbonate) and sulfates, and leaves remaining an aqueoussolution to which other sources of divalent cations may be added forfurther precipitation (i.e., more waste gas may be cycled through it tocause more precipitation material).

In various embodiments, adjustments of the parameters described hereinfor precipitation may be used to optimize the amount of a particularcomponent that is trapped, or precipitated, or both precipitated andtrapped in precipitation material. It will be appreciated that in someembodiments it is desired not to precipitate or trap a component of thewaste gas stream or to minimize such trappings. Thus, in someembodiments, conditions may be adjusted to decrease, minimize, orsubstantially eliminate the inclusion of one or more components of thewaste gas stream in the precipitation material. Such components mayinclude one or more of the components described herein (e.g., mercury,other heavy metals, radioactive substances, and the like).

Regardless of when the waste gas stream is contacted with the aqueoussolution, in some instances when the waste gas stream is contacted withthe aqueous solution, the aqueous solution is not exceedingly alkaline,such that the solution may have a pH of pH 10 or lower, or pH 9.5 orlower, or pH 9 or lower, or even pH 8 or lower. In some embodiments, theaqueous solution contacted with the waste gas stream is not a aqueoussolution that has first been made basic (e.g., from the addition ofproton-removing agents or from an electrochemical protocol). In someembodiments, the aqueous solution that is contacted with the waste gasstream is not an aqueous solution that has been made basic by additionof proton-removing agents such as hydroxides (e.g., sodium hydroxide).In some embodiments, the aqueous solution is one that has been made onlyslightly alkaline, such as by addition of an amount of proton-removingagent such as an oxide (e.g., calcium oxide, magnesium oxide, etc.).

Following precipitation of precipitation material (e.g., carbonates,sulfates, sulfites, and/or the like) from the aqueous solution, theresultant precipitation material may be separated. Separation of theprecipitation material may be achieved using any of a number ofconvenient approaches, including draining (e.g., gravitationalsedimentation of the precipitation material followed by draining),decanting, filtering (e.g., gravity filtration, vacuum filtration,filtration using forced air), centrifuging, pressing, or any combinationthereof. For example, separation of the precipitation material may beachieved as described in U.S. Provisional Patent Application No.61/168,166, filed 9 Apr. 2009, which is incorporated herein byreference. Separation of bulk water from the precipitation materialproduces a concentrated composition of precipitation material, whereinthe concentrated composition is concentrated with respect to carbonatesand/or bicarbonates, and any other co-products resulting from processingan industrial waste gas stream. The concentrated composition may also beconsidered dewatered precipitation material or a wet cake ofprecipitation material depending upon the degree of water removed. Insome embodiments, the concentrated composition comprises at least 10%,15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%,85%, 90%, 95%, 99% precipitation material (i.e., solids) with thebalance being water or a solution thereof.

The precipitation material may also be isolated with a liquid-solidseparator (222) of treatment system 220 to produce a wet cake ofprecipitation material and a supernatant as shown in FIG. 2A, which isillustrative and in no way limits the following description to FIG. 2A.(See also U.S. Provisional Patent Application No. 61/168,166, filed 9Apr. 2009, which is incorporated herein by reference in its entirety.)In some embodiments the precipitation material is not separated, or isonly partially separated. In such embodiments, the supernatant,optionally including some or all of the precipitation material, may bedisposed of by any suitable means. In some embodiments, a compositioncomprising the supernatant and, optionally, some or all of theprecipitation material, may be transported (e.g., by a) to a land- orwater-based location and placed at that location. For example, in suchembodiments, the composition, including supernatant relatively fee ofprecipitation material, may be disposed above ground, underground, inwater (e.g., ocean), underwater, or the like, as such compositions aresuitable (e.g., meet permitted discharge limits of United StatesEnvironmental Protection Agency and/or state environmental agencies,such as National Pollutant Discharge Elimination System (NPDES) limits,as such discharge limits exist on the filing date of this patentapplication) for release into the environment. This is especially usefulin embodiments where the source of divalent cations is seawater, as theconcentration of sulfates in seawater may be far greater than theconcentration of sulfates in compositions of the invention. As such, theadded sulfates would negligibly increase the concentration of sulfatesin the seawater. It will be appreciated that the carbon footprint,amount of energy used, and/or amount of combustion gases produced forsequestering a given amount of combustion gases from an industrialexhaust gas may be minimized in a process where no further processingbeyond disposal occurs with the precipitation material.

The precipitation material resulting from separation (e.g., resultantdewatered precipitation material) may then be dried to produce a raw,dried product using a dryer (224) as shown in FIG. 2A, which isillustrative and in no way limits the following description to FIG. 2A.For example, drying may be achieved by air-drying the precipitationmaterial. In embodiments in which the precipitation material is airdried, air-drying may be done at room or elevated temperature. Incertain embodiments, the elevated temperature is provided by the wastegas stream of the industrial plant. In these embodiments, the waste gasstream (e.g., flue gas) from the power plant may be first used in thedrying step, where the waste gas stream may have a temperature rangingfrom 30 to 700° C., such as 75 to 300° C. The waste gas stream may becontacted directly with wet precipitation material in the drying stage,or used to indirectly heat gases (such as air) in the drying stage. Thedesired temperature may be provided in the waste gas stream by havingthe gas conveyor, e.g., duct, from the industrial plant originate at asuitable location, e.g., at a location a certain distance in the HRSG orup the flue, as determined based on the specifics of the exhaust gas andconfiguration of the industrial plant. In some embodiments, theprecipitation material may be spray dried to dry the precipitationmaterial, wherein a slurry comprising the precipitation material may bedried by feeding it through a hot gas (e.g., waste gas stream from thepower plant). For example, the slurry comprising the precipitationmaterial may be pumped through an atomizer into a main drying chamberand a hot gas may be passed as a co-current or counter-current to theatomizer direction. In certain embodiments, drying is achieved byfreeze-drying (i.e., lyophilization), where the precipitation materialis frozen, the surrounding pressure is reduced and enough heat is addedto allow the frozen water in the material to sublime directly from thefrozen precipitation material to gas. Depending on the particular dryingprotocol of the system, the dryer may include a filtration element,freeze-drying structure, spray-drying structure, etc.

In some embodiments, the dewatered precipitation material or wet cakemay be washed before drying, as shown at optional washer (226) of FIG.2A, which is illustrative and in no way limits the following descriptionto FIG. 2A. The dewatered precipitation material or wet cake may bewashed with freshwater to remove salts (such as NaCl) from the material.Spent wash water may be disposed of as convenient, for example, bydisposal in a tailings pond, etc. Thereafter, as illustrated, the washedprecipitation material or washed wet cake may be dried in a dryer 224 toprovide for desired physical characteristics in the raw, dried productsuch as particle size, surface area, etc. During drying, or sometimethereafter, one or more components may be added to the precipitationmaterial such as admixtures, aggregate, supplementary cementitiousmaterials, etc., to produce additional products.

The dried product (e.g., dried precipitation material) may be disposedof in a number of different ways. In certain embodiments, the driedproduct is transported to a location for long-term storage, effectivelysequestering combustion gases (e.g., CO₂, SOx, NOx, etc.) andparticulate matter in a storage-stable form (e.g., a combustiongas-sequestering material that may be stored above ground). For example,the precipitation material may be stored at a long-term storage siteadjacent to the industrial plant and precipitation system. In yet otherembodiments, the precipitation material may be transported and placed atlong term storage sites, e.g., above ground, below ground, etc. asdesired, where the long term storage site is distal to the power plant(which may be desirable in embodiments where real estate is scarce inthe vicinity of the power plant). In these embodiments, where theprecipitation material is transported to a long-term storage site, itmay be transported in empty conveyance vehicles (e.g., barges, traincars, trucks, etc.) that were employed to transport the fuel or othermaterials to the industrial plant and/or precipitation plant. In thismanner, conveyance vehicles used to bring fuel to the industrial plant,materials to the precipitation plant (e.g., alkali sources), and thelike may be employed to transport precipitation material, and thereforesequester combustion gases from the industrial plant.

In some embodiments, compositions of the invention (e.g., solution,slurry, precipitation material, etc.) may be disposed of in anunderwater or underground location, the choice of which may varydepending upon location and available resources. Compositions may beuntreated (e.g., no water removed), treated to remove a portion ofsupernatant to produce a concentrated composition, dried (e.g.,spray-dried precipitation material), or any such form described herein,including compositions comprising primarily supernatant. Underwaterlocations include, but are not limited to, inland underwater locations(e.g., under a freshwater lake) or ocean (or sea) underwater locations.The underwater location may be shallow including locations that are 1000feet or less, such as 200 feet or less, including 150 feet or less, ordeep, including locations that are 200 feet or more, such as 500 feet ormore, 1000 feet or more, 2000 feet or more, including 5000 feet or more.Underground locations include any subterranean site (e.g., geologicalformation) of suitable impermeability and stability for long-termstorage of compositions of the invention. A composition of the inventionmay be injected into an underground location that is 50 meters or more,100 meters or more, 200 meters or more, 500 meters of more, or 1000meters or more below the surface of the Earth. In some embodiments, thecomposition is injected into an underground location that is less than3000 feet, less than 2500 feet, less than 2000 feet, less than 1500feet, less than 1000 feet, less than 500 feet, less than 250 feet, orless than 100 feet below the surface of the Earth. In some embodiments,the composition is injected into a geological formation from which anaqueous brine was removed. A composition conveyor (e.g., pipe, duct,etc. configured with suitable pumps, etc.) configured to transportcompositions of the invention (e.g., solution, slurry, precipitationmaterial, etc.) may be used to effect disposal of compositions of theinvention underwater or underground.

Where desired, the compositions made up of the precipitation materialand the mother liquor may be stored for a period of time followingprecipitation and prior to disposal. For example, the composition may bestored for a period of time ranging from 1 to 1000 days or longer, suchas 1 to 10 days or longer, at a temperature ranging from 1 to 40° C.,such as 20 to 25° C.

In some embodiments of the invention nearly 100% of the NOx, SOx, and/orCO₂ contained in a flue gas from a power plant is sequestered in astable mineral; this may be done in a single precipitation step (e.g.,in a single processor) or in multiple precipitation steps (e.g., inmultiple processors configured in series, parallel, or a combinationthereof), and may further involve other processes for sequestering CO₂,e.g., as the concentration of CO₂ is decreased in the flue gas, moreenergy-intensive processes that be prohibitive in energy consumption forremoving all of the original CO₂ in the gas may become practical inremoving the final CO₂ in the gas. Thus, in some embodiments, the gasentering the power plant (ordinary atmospheric air) may contain aconcentration of CO₂ that is greater than the concentration of CO₂ inthe flue gas exiting the plant that has been treated by the processesand systems of the invention. Hence, in some embodiments, the methodsand systems of the invention encompass a method comprising supplying agas, e.g., atmospheric air, to a power plant, where the gas comprisesCO₂; treating the gas in the power plant, e.g., by combustion of fossilfuel to consume O₂ and to produce CO₂ then treating exhaust gas toremove CO₂; and releasing gas from the power plant, where the gasreleased from the power plant has a lower CO₂ content than the gassupplied to the power plant. In some embodiments, the gas released fromthe power plant contains at least 10% less CO₂, or at least 20% lessCO₂, or at least 30% less CO₂, or at least 40% less CO₂, or at least 50%less CO₂, or at least 60% less CO₂, or at least 70% less CO₂, or atleast 80% less CO₂, or at least 90% less CO₂, or at least 95% less CO₂,or at least 99% less CO₂, or at least 99.5% less CO₂, or at least 99.9%less CO₂, than the gas entering the power plant; in some embodiments thegas entering the power plant is atmospheric air and the gas exiting thepower plant is treated flue gas.

FIG. 2B, which is illustrative and in no way limits the followingdescription to FIG. 2B, shows an embodiment of the system 200Bconfigured such that a waste gas stream (e.g., combustion gas stream)may be selectively treated with one or more emission controltechnologies to remove one of more of the components (e.g., SOx, NOx,particulate matter, etc.) of the flue gas before the flue gas isintroduced into the processor 210. Thus, as illustrated in FIG. 2B, at232, in one embodiment, nitrogen oxide gases (NOx) may be removed fromthe waste gas stream before the waste gas stream is sent to theprocessor (210) (e.g., reactor); alternatively, by utilizing 232 and234, both NOx and fly ash may be removed from the waste gas stream;similarly, by 232, 234, and 236, three components of the waste gasstream (NOx, fly ash, and SOx) may be removed before the gas isintroduced into the processor.

As will be appreciated, the system as illustrated in FIG. 2B, as withany system of the invention, may accommodate optional NOx controltechnology (232) (e.g., selective catalytic reduction (SCR),non-selective catalytic reduction, etc.), optional particulate mattercontrol technology (234) (e.g., electrostatic precipitator (ESP), fabricfilter, etc.), and optional SOx control technology (236) (e.g., flue gasdesulfurization (FGD), etc.), and, when present, emission controltechnology may be configured in any order to remove any desiredcomponents of the waste gas stream. Systems of the invention may befurther configured to accommodate specific mercury control technologies(e.g., activated carbon injection (ACI)) as well. Systems may be builtfrom the ground up to comprise such optional emission controltechnology, or existing industrial plants with emission controltechnology may be retrofitted with CO₂-processing systems. Whether ornot an industrial plant coupled with a CO₂-processing system is builtfrom the ground up or retrofitted, emissions from the industrial plant,the CO₂-processing system, or a combination of the industrial plant andthe CO₂-processing system are designed to meet or improve upon emissioncontrol standards selected from the group consisting of ReasonablyAvailable Control Technology (RACT); Best Available Control Technology(BACT); Maximum Achievable Control Technology (MACT); Lowest AchievableEmission Rate (LAER); and/or any United States Environmental ProtectionAgency (EPA) reference methods, as such emission control standards existon the filing date of this patent application.

In some embodiments, systems of the invention comprise no NOx, SOx, orparticulate matter control technology. For example, in such embodiments,a waste gas stream may be directly passed to a processor, optionallyafter cooling the waste gas stream with a heat exchanger. In someembodiments, systems of the invention comprise one emission controltechnology selected from the group consisting of NOx, SOx, orparticulate matter control technology. For example, in such embodiments,the system may comprise NOx control technology. For example, in otherembodiments, the system may comprise particulate matter controltechnology. In some embodiments, systems of the invention comprise twoemission control technologies selected from the group consisting of NOx,SOx, or particulate matter control technology. For example, in suchembodiments, the system may comprise NOx and particulate matter controltechnology, wherein the NOx control technology is placed before theparticulate matter control technology. For example, in otherembodiments, the system may comprise NOx and particulate matter controltechnology, wherein the particulate matter control technology is placedbefore the NOx control technology. In some embodiments, systems of theinvention comprise NOx, SOx, and particulate matter controltechnologies. For example, in such embodiments, the system may compriseNOx, SOx, and particulate matter control technologies, wherein the NOxcontrol technology is placed before the particulate matter controltechnology. For example, in other embodiments, the system may compriseNOx, SOx, and particulate matter control technologies, wherein theparticulate matter control technology is placed before the NOx controltechnology. Heat exchangers may be used as appropriate in the system tobring the temperature of the flue gas down to an appropriate temperaturefor the emission control technology. For example, heat exchangers may beused to bring the temperature down to the appropriate temperature rangefor efficient scrubbing of NOx in a NOx control technology or SOx in aSOx control technology. Furthermore, any of the emission controltechnologies may be configured to provide material for the purpose ofprocessing CO₂. For example, in some embodiments, a particulate mattercontrol technology (e.g., electrostatic precipitator, fabric filter,etc.) may be configured to provide collected particulate matter such asfly ash (e.g., an industrial waste source of proton-removing agentsand/or divalent cations) to a processor of the invention (a front-endaddition of fly ash). In some embodiments, a particulate matter controltechnology (e.g., electrostatic precipitator, fabric filter, etc.) maybe configured to provide collected particulate matter such as fly ash toa composition (e.g., supplementary cementitious material, a blend ofPortland cement with a supplementary cementitious material, etc.) of theinvention (a back-end addition of fly ash). Such uses of fly ash (e.g.,replacement of a portion of cement or cementitious material) are knownin the art.

Systems of the invention and systems in combination with variousindustrial plants may meet or improve upon pollution control standardssuch as Reasonably Available Control Technology (RACT); Best AvailableControl Technology (BACT); Maximum Achievable Control Technology (MACT);Lowest Achievable Emission Rate (LAER); and/or any United StatesEnvironmental Protection Agency (EPA) reference methods, as suchpollution control standards exist on the filing date of this patentapplication. Meeting or improving upon such pollution control standardsare possible when a CO₂-processing system of the invention captures atleast 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 99%, or 99.9% ofthe CO₂ being emitted by the industrial plant (e.g., coal-fired powerplant). As systems of the invention are effective at meeting orimproving upon pollution control standards, CO₂-processing systems ofthe invention may even be shut down for a short period of time (e.g.,hours, days, etc.) for maintenance or during periods of high demand(e.g., high energy demand) and still meet or improve upon pollutioncontrol standards such as RACT, BACT, MACT, LAER; and/or any UnitedStates Environmental Protection Agency (EPA) reference methods, as suchpollution control standards exist on the filing date of this patentapplication. For example, high energy demand at a coal-fired power plantmay require the power plant to utilize reserve capacity (e.g., 10%reserve capacity) and/or the energy reserved for operation of aCO₂-processing system of the invention. In such a scenario, theCO₂-processing system may be powered down and emissions (e.g., CO₂, SOx,Hg, etc.) that would otherwise be processed by the system would bereleased to the atmosphere, optionally through other emission controltechnologies (e.g., NOx, particulate matter, and/or SOx controltechnologies), if such emission control technologies are present. Sincethe coal-fired power plant might only be run for a few hours a yearwithout a CO₂-processing system of the invention controlling emissions,the power plant may still meet or improve upon pollution controlstandards. Additional money would not need to be spent for sparecapacity and increases in pollution during such spare capacityoperation.

Systems of the invention, including systems such as that shown in FIG.2, may be configured to effect oxidation of components in the waste gasstream. Oxidation of components in the waste gas stream comprisessubjecting the waste gas stream to hydrogen peroxide (H₂O₂) or aH₂O₂/CH₃OH mixture as described above. An exemplary description ofsystems and methods for oxidizing a CO₂-containing gaseous stream usinghydrogen peroxide may be found in U.S. Pat. No. 5,670,122, which isincorporated herein by reference in its entirety. A gaseous stream maybe treated with hydrogen peroxide for a sufficient time to oxidizecomponents therein, for example, to convert one or more of nitric oxide(NO), sulfur trioxide (SO₃), light hydrocarbons (C₁-C₄), carbon monoxide(CO) and mercury to NO₂, SO₂, CO₂ and HgO, respectively. The gaseousstream may be treated with a hydrogen peroxide or a H₂O₂/CH₃OH mixtureprior to contacting the gaseous stream with an aqueous solution (e.g.,an aqueous solution comprising divalent cations, proton-removing agents,or a combination thereof). In some embodiments, a processed waste gasstream, recovered after contacting a gaseous stream with an aqueoussolution, may be treated with a H₂O₂/CH₃OH mixture and reprocessed in aprocessor of the invention to capture any remaining components of thewaste gas stream.

The reaction time of the hydrogen peroxide or H₂O₂/CH₃OH mixture may bein the range from about 0.01 to about 5 seconds, for example, from about0.1 to about 2 seconds. The NO₂, SO₂, CO₂, and HgO (and other componentsof the waste gas stream) may then be removed by absorption into anaqueous solution (e.g., an aqueous solution comprising divalent cations,proton-removing agents, or a combination thereof). In some embodiments,CO₂-charged solution may then subjected to the precipitation conditionsto form precipitation material comprising one or more of the componentsfrom the gaseous stream (e.g., NO₂, SO₂, CO₂, HgO, etc.). As such, theinvention provides a quick and efficient method for removing a widevariety of components from a waste gas stream (e.g., CO₂, criteriapollutants, and/or other toxic or environmentally harmful components)such that the components are not emitted to the atmosphere indangerously high concentrations. For example, the invention may be usedto remove these components from waste gas streams (e.g., flue gases)emanating from boilers, furnaces, incinerators, stationary engines, andother systems for combustion of various types of fuels.

As described above the molar ratio of injected H₂O₂ (MeOH) to totalpollutants may be 0.01 to 5.0, such as 0.1 to 4.0, including 0.1 to 3.0,for example, 0.1 to 2.0, 0.1 to 1.0, or 0.1 to 0.5. Such ratios may alsobe effective when aqueous H₂O₂ or aqueous H₂O₂ in methanol is used. Insome embodiments, for example, the molar ratio of injected H₂O₂ (MeOH orH₂O) to total pollutants may be 0.5 to 2.0. In some embodiments, forexample, the molar ratio of injected H₂O₂ (MeOH or H₂O) to totalpollutants may be 0.9 to 1.5. Hydrogen peroxide may be injected (e.g.,in the form of a methanolic or aqueous solution) at a concentration of1% to 50%, for example, from 10% to about 30%.

The use of hydrogen peroxide in systems and methods of the invention hasmany advantages. If properly stored, hydrogen peroxide solutions arevery stable. The use of hydrogen peroxide does not pose anyenvironmental problems since hydrogen peroxide is not itself a source ofpollution, and the only reaction by-products are water and oxygen.Therefore, hydrogen peroxide can be used safely in the invention.

Referring to FIG. 2C, which is illustrative and in no way limits thefollowing description to FIG. 2C, in one embodiment, a system 200Ccomprises a processor (210) comprising a gas-liquid or gas-liquid-solidcontactor adapted for contacting a carbon dioxide-rich waste gas stream230 with an aqueous cation solution comprising divalent cations 250 tocause neutralization of constituents in a waste stream 240, and to forma carbonate-containing precipitation material with the cations in theaqueous solution. As illustrated, the system includes a source ofproton-removing agents 240 (e.g., OH⁻) contained in the waste source. Invarious embodiments the OH⁻ in the waste source is utilized to adjustthe pH of the aqueous solution to promote the absorption of thecombustion gases (e.g., carbon dioxide, NOx and SOx) in the solution,and to cause components in the waste gas stream to react with thecations in the solution to form a carbonate-containing precipitationmaterial in the solution. Examples of suitable waste streams include redmud containing sodium hydroxide and fly ash containing calcium oxide.

In various embodiments, the interaction of the waste gas stream 230 withthe solution 250 in the processor 210 results in formation of a slurrycomprising particulate matter from the waste gas stream andprecipitation material formed from the gases interacting with cations inthe solution. In various embodiments, the slurry is directed to aliquid-solid separator 222 where, as in shown in FIGS. 2A and 2C, whichare merely illustrative of the invention described herein, it isseparated into a concentrated composition (e.g., wet cake) and asupernatant. In various embodiments, as illustrated in FIG. 2C, forexample, the supernatant, depleted of divalent cations, hydroxide ionsand precipitation material, is forwarded to desalination. In otherembodiments, optionally at least a portion of the supernatant isreplenished with alkaline earth metal cations and proton-removing agentsand re-circulated to the processor 210. Optionally, as shown in FIG. 2A,which is illustrative and in no way limits the following description toFIG. 2A, the wet cake from the liquid-solid separator 222 is washed in awashing station 226 with clean water to remove soluble salts from thewet cake to produce a desalinated wet cake and wash water. From thewashing station, the wet cake may be dried in a dryer 224 to form a raw,dried product. As above, the raw, dried product, in turn, may be refinedin a refinery to produce a refined product. Raw, dried product orrefined product may be used to prepare building materials of theinvention in a manufacturing system (228) depending upon thespecification of the building material. Building materials may includecement, fine aggregate, mortar, coarse aggregate, concrete, pozzolan, ora combination thereof, further described in U.S. patent application Ser.No. 12/126,776, filed 23 May 2008; U.S. patent application Ser. No.12/344,019, filed 24 Dec. 2008; U.S. patent application Ser. No.12/475,378, filed 29 May 2009; and U.S. patent application Ser. No.12/604,383, filed 22 Oct. 2008, each of which is incorporated herein byreference.

Systems of the invention, as shown in FIG. 2C, which is illustrative andin no way limits the following description to FIG. 2C, equipment thatcan be used to neutralize the waste components and produce a buildingproduct from the resulting precipitation material are commerciallyavailable but may need customization. Also, as shown, the system 200C invarious embodiments comprises a waste source 240 of proton-removingagents (e.g., OH⁻) for supplying hydroxide ions to cause formation ofprecipitation material in the processor 210. Although in the embodimentof FIG. 2C source of proton-removing agents (e.g., OH⁻) is available inthe waste stream 240, red mud, fly ash, or any convenient source ofproton-removing agents may be used (e.g., commercially available sodiumhydroxide). Thus, in one embodiment, the system includes anelectrochemical system for supplying hydroxide ions to the aqueouscation solution as described above with reference to FIG. 2A, and as isillustrated in FIG. 3, and as is described in commonly assignedInternational Patent Application No. PCT/US08/088,242, filed 23 Dec.2008, which is incorporated herein by reference in its entirety.

With reference to FIG. 2C, which is illustrative and in no way limitsthe following description to FIG. 2C, the waste gas stream 230comprising combustion gas is contacted with the divalent cation aqueoussolution to produce a gas-charged aqueous solution. By gas-chargedaqueous solution is meant an aqueous cation solution comprisingcombustion gases, wherein combustion gas molecules have combined withwater molecules to produce a new chemical species, e.g., carbonic acid,hydrochloric acid, nitric acid, sulfuric acid, bicarbonate, carbonate,or where the combustion gas molecules have merely dissolved in thewater. A gas-charged water also includes an aqueous solution comprisingparticulate matter entrained in the aqueous solution from the combustiongases. In various embodiments the combustion gases include carbondioxide and carbon monoxide (COx); nitrogen oxides (NOx); sulfur oxides(SOx) and sulfides; halides such as hydrogen chloride and hydrogenfluoride, which may also be considered acid gases along with, forexample, SOx (e.g., SO₃, SO₂); particulate matter such as fly ash, dustsand metals including arsenic, beryllium, boron, cadmium, chromium,chromium VI, cobalt, lead, manganese, mercury, molybdenum, selenium,strontium, thallium, and vanadium; and organics such as hydrocarbons,radioactive materials, dioxins, and PAH compounds. In variousembodiments, the invention provides a system adaptable for treating aninput combustion gas stream comprising all, or one, or more than one ofthese components simultaneously.

Charging the aqueous cation solution in a processor (e.g., processor 210of FIG. 2C) results in an increase in the combustion gas content in theaqueous solution, e.g., in the form of carbonic acid, bicarbonate,and/or carbonate ion, and a decrease in concentration of outlet gasesthat exits the processor. In various embodiments, the combustiongas-charged aqueous solution is acidic, having a pH of 6 or less, suchas 5 or less and including 4 or less. In certain embodiments, theconcentration of CO₂, NOx and/or SOx of the gas that is used to chargethe water is 0.1%, 1%, 5%, 10% or higher, 25% or higher, including 50%or higher, such as 75% or even higher. Contact protocols of interestinclude, but are not limited to: direct contacting protocols, e.g.,bubbling the gas through the volume of the aqueous solution, concurrentcontacting and mixing, e.g., contact between unidirectional flowinggaseous and liquid phase streams, countercurrent means, e.g., contactbetween oppositely flowing gaseous and liquid phase streams, and thelike. Thus, contact may be accomplished through use of infusers,bubblers, fluidic Venturi reactor, sparger, gas filter, spray, tray,flat stream or packed column reactors, and the like, as may beconvenient and as described in U.S. Pat. No. 7,379,487, which isincorporated herein by reference in its entirety. In various embodimentsthe gas may be processed before being used to charge the aqueoussolution. For example, the gas may be subjected to oxidation conditions,e.g., to convert CO to CO₂, NO to NO₂, and SO₂ to SO₃, as desired asdescribed for example in U.S. Pat. No. 5,670,122, which is incorporatedherein by reference in its entirety.

With reference to FIG. 2C, which is illustrative and in no way limitsthe following description to FIG. 2C, at processor 210, carbonatecompounds, sulfate and sulfite compounds that may be amorphous orcrystalline, are precipitated. Where the waste source 240 comprises asolid waste that does not dissolve in the aqueous solution (e.g. red mudor fly ash), the base in the waste may be neutralized and precipitationmaterial may thus contain neutralized solids, e.g., neutralized red mudor fly ash as appropriate. Precipitation conditions include those thatchange the physical environment of the aqueous solution to produce thedesired precipitation material. For example, the temperature of thewater may be raised to an amount suitable for precipitation of thedesired carbonate or sulfate compound(s) to occur. In such embodiments,the temperature of the water may be raised to a value from 5 to 70° C.,such as from 20 to 50° C. and including from 25 to 45° C. As such, whilea given set of precipitation conditions may have a temperature rangingfrom 0 to 100° C., the temperature may be raised in certain embodimentsto produce the desired precipitation material. In certain embodiments,the temperature is raised using energy generated from low or zero carbondioxide emission sources, e.g., solar energy source, wind energy source,hydroelectric energy source, and the like.

FIGS. 4-11 illustrate various embodiments of methods of the inventionwhereby a waste gas stream may be treated to remove combustioncomponents and form a composition (e.g., precipitation material). Insome embodiments, the method provides for trapping at least twocomponents of an industrial waste gas, e.g., a flue gas, in a solidform, e.g. precipitating the component or a derivative of the componentfrom an aqueous solution, or physically trapping the component or aderivative of the component in a precipitation material or other solidform, or a combination of precipitation and trapping. Components mayinclude CO₂, CO, SOx, NOx, mercury, arsenic, lead, selenium, fluorine,chlorine, hydrogen chloride, hydrogen fluoride, particulate matter(e.g., fly ash), and hydrocarbons. In some embodiments, at least 10, 20,30, 40, 50, 60, 70, 80, 90, 95, or 99% of the CO₂, if present, isremoved from the industrial waste gas. In some embodiments, at least 10,20, 30, 40, 50, 60, 70, 80, 90, 95, or 99% of the CO, if present, isremoved from the industrial waste gas. In some embodiments, at least 10,20, 30, 40, 50, 60, 70, 80, 90, 95, or 99% of the SOx, if present, isremoved from the industrial waste gas. In some embodiments, at least 10,20, 30, 40, 50, 60, 70, 80, 90, 95, or 99% of the NOx, if present, isremoved from the industrial waste gas. In some embodiments, at least 10,20, 30, 40, 50, 60, 70, 80, 90, 95, or 99% of the mercury, if present,is removed from the industrial waste gas. In some embodiments, at least10, 20, 30, 40, 50, 60, 70, 80, 90, 95, or 99% of the arsenic, ifpresent, is removed from the industrial waste gas. In some embodiments,at least 10, 20, 30, 40, 50, 60, 70, 80, 90, 95, or 99% of the lead, ifpresent, is removed from the industrial waste gas. In variousembodiments, at least 10, 20, 30, 40, 50, 60, 70, 80, 90, 95, or 99% ofthe components of the combustion gas is removed from the waste gasstream.

Thus, in some embodiments the invention provides a process for treatingan industrial waste gas that contains CO₂ and SOx, wherein the processremoves at least 10, 20, 30, 40, 50, 60, 70, 80, 90, 95, or 99% of theCO₂, and at least 10, 20, 30, 40, 50, 60, 70, 80, 90, 95, or 99% of theSOx, e.g., by trapping the CO₂ and SOx, or derivatives of one or both,in a solid form, such as a precipitation material from an aqueoussolution. In some embodiments the invention provides a method fortreating an industrial waste gas that contains CO₂ and SOx, wherein theprocess removes at least 10% of the CO₂, and at least 10, 20, 30, 40,50, 60, 70, 80, 90, 95, or 99% of the SOx. In some embodiments theinvention provides a process for treating an industrial waste gas thatcontains CO₂ and SOx, wherein the process removes at least 30% of theCO₂, and at least 10, 20, 30, 40, 50, 60, 70, 80, 90, 95, or 99% of theSOx. In some embodiments the invention provides a process for treatingan industrial waste gas that contains CO₂ and SOx, wherein the processremoves at least 50% of the CO₂, and at least 10, 20, 30, 40, 50, 60,70, 80, 90, 95, or 99% of the SOx. In some embodiments the inventionprovides a process for treating an industrial waste gas that containsCO₂ and SOx, wherein the process removes at least 70% of the CO₂, and atleast 10, 20, 30, 40, 50, 60, 70, 80, 90, 95, or 99% of the SOx.

In some embodiments, a waste gas stream may be pre-treated (e.g., asdescribed in reference to FIG. 2B) to increase the solubility, oxidationstate, or other properties of one or more of the waste gas components inorder to make one or more of the components more amenable to theprocesses of the invention (e.g., precipitation or otherwise entrappingthe component in a stable solid form). In such embodiments,pre-treatment may occur in one step or more than one step, for example,in 2, 3, 4, 5, 6, 7, 8, 9, 10, or more than 10 pre-treatment steps. Insome embodiments of the invention, the waste gas stream is notpre-treated. In some embodiments, the waste gas stream is pre-treatedwith a particulate matter control technology (e.g., electrostaticprecipitator, fabric filter, etc.) to remove particulate matter such asfly ash.

Particulate matter, e.g. fly ash, may be removed at the stage ofprecipitation, or may be removed separately from the industrial gasbefore the precipitation reaction, or a combination of the two, e.g.,some particulate matter is removed and the remaining particulate matteris precipitated. In some embodiments, particulate matter may be addedback to the precipitation material. For example, in some embodiments,the precipitation material is processed to become a building material,such as cement, and particulate matter (e.g., fly ash) may be added tothe precipitation material, as is sometimes practiced in the industry.

With reference to FIG. 4, in one embodiment the method in step 400comprises: contacting the waste gas stream with a metal ion-containingaqueous solution, whereby at least three of the following components areremoved from the waste gas stream and contained in an insoluble stableprecipitation material: carbon dioxide; carbon monoxide; nitrogen oxides(NOx); sulfur oxides (SOx); hydrogen sulfide; hydrogen chloride;hydrogen fluoride; fly ash; dusts; metals including arsenic, beryllium,boron, cadmium, chromium, chromium VI, cobalt, lead, manganese, mercury,molybdenum, selenium, strontium, thallium; hydrocarbons; radioactivematerials, dioxins, and PAH.

In another embodiment as illustrated in FIG. 5, the method in step 500comprises: contacting a waste gas stream comprising carbon dioxide,nitrogen oxides, and sulfur oxides with a metal ion-containing aqueoussolution and causing precipitation of a precipitation material thatcomprises carbon dioxide, sulfur oxide and mercury from the waste gasstream.

In another embodiment as illustrated in FIG. 6, the method in step 600comprises contacting a flue gas from an industrial source with a metalion-containing aqueous solution under conditions that cause theprecipitation of carbon dioxide and at least two other components of theflue gas into an insoluble stable precipitation material.

In another embodiment as illustrated in FIG. 7, the method in step 700comprises treating a flue gas from an industrial source to removeundesirable components of the flue gas, by: treating the flue gas toremove particulate matter then treating the flue gas to remove carbondioxide, mercury oxides and sulfur oxides therefrom.

In another embodiment as illustrated in FIG. 8, the method in step 800comprise treating a waste gas stream comprising carbon dioxide, mercuryand sulfur oxides, to remove at least 50% of the carbon dioxide and atleast 50% of the sulfur oxides from the waste gas stream byprecipitating in a single step the carbon dioxide and sulfur oxides inan insoluble composition.

In another embodiment as illustrated in FIG. 9, the method in step 900comprises treating a waste gas stream comprising carbon dioxide andmercury, to remove at least 50% of the carbon dioxide and at least 50%of the mercury in a single process that comprises precipitating thecarbon dioxide and mercury.

In another embodiment, the method comprises treating a flue gas from anindustrial source to remove undesirable components of the flue gas,comprising treating the flue gas to remove particulate matter thentreating the flue gas to remove both carbon dioxide and sulfur oxides(SOx).

With reference to FIG. 10, the method in one embodiment at step 1000comprises: comprising contacting a first waste stream with a secondwaste stream in the presence of a divalent cation-containing aqueoussolution whereby pollutants in at least one of the waste streams areneutralized. In various embodiments, at least one of the waste streamscomprises carbon dioxide and other combustion gases, and the aqueousdivalent cation solution comprises calcium and/or magnesium ions. Invarious embodiments, the non-gaseous waste stream comprises an availablebase, e.g., hydroxide ions as in red mud, or calcium oxide in coal ash.In various embodiments, a precipitation material comprising calciumand/or magnesium carbonate and neutralized constituents of the waste isobtained in the divalent cation solution as described herein. In variousembodiments, the precipitation material with the neutralized waste maybe disposed and/or can be utilized with the carbonate-containingprecipitation material as a building product as described herein.

With reference to FIG. 11, in another embodiment, the method in step1100 comprises a step of neutralizing an industrial waste, comprising:contacting the waste with a waste gas stream comprising carbon dioxide,and a liquid stream comprising an aqueous divalent cation solution,whereby the pH of the waste is neutralized. As with the method of FIG.10, the method FIG. 11 includes treating a waste stream comprising redmud and/or fly ash, by reacting it with an aqueous divalent cationsolution comprises alkaline earth metal ions, e.g., divalent cationsolution comprising calcium and/or magnesium ions available in asaltwater such as seawater, brackish water, brine or an aqueous solutioncomprising dissolved mafic minerals. In another embodiment, the methodincludes utilizing a waste gas stream comprising carbon dioxide formedby combusting fossil fuels, to precipitate a carbonate in the aqueousdivalent cation solution.

In various embodiments, the carbonate-containing precipitation materialmay include divalent cation carbonates such as calcium carbonate,magnesium carbonate, calcium magnesium carbonate. In variousembodiments, the precipitation material may are precipitated with one ormore of the following constituents: red mud, fly ash, dusts, metalsincluding arsenic, beryllium, boron, cadmium, chromium, chromium VI,cobalt, lead, manganese, mercury, molybdenum, selenium, strontium, andthallium. In one embodiment, the waste gas stream is processed before orafter contact with the solution to remove one or more of particulatematter and nitrogen oxides. In another optional step, the methodincludes extracting a supernatant liquid and a desalinated water fromthe aqueous solution, and circulating at least a portion of thesupernatant liquid to the aqueous solution. In various embodiments,substantially all the waste from a particular waste stream e.g., carbondioxide, mercury and/or sulfur oxides are removed e.g., removing 5%,10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% or more of hydroxide ions fromthe waste.

Compositions

Compositions of the invention may be solutions, solids, or multiphasicmaterials (e.g., slurries) comprising carbonates, bicarbonates, orcarbonates and bicarbonates, optionally of divalent cations such asCa²⁺, Mg²⁺, or combination thereof. The amount of carbon in suchcompositions (e.g., precipitation material) produced by methods of theinvention may vary. In some embodiments, compositions comprise an amountof carbon (as determined by using protocols described in greater detailbelow) ranging from 1% to 15% (w/w), such as 5 to 15% (w/w), including 5to 14% (w/w), 5 to 13% (w/w), 6 to 14% (w/w), 6 to 12% (w/w), and 7 to12% (w/w), wherein a substantial amount of the carbon may be carbon thatoriginated (as determined by using protocols described in greater detailbelow) from the source of CO₂. In such embodiments, 10 to 100%, such as50 to 100%, including 90 to 100% of the carbon present in thecomposition (e.g., precipitation material) is from the source of CO₂(e.g., industrial waste gas stream comprising carbon dioxide). In someinstances, the amount of carbon present in the composition that istraceable to the carbon dioxide source is 50% or more, 60% or more, 70%or more, 80% or more, 90% or more, 95% or more, 99% or more, including100%.

Compositions of the invention (e.g., precipitation material comprisingcarbonates, bicarbonates, or carbonates and bicarbonates) may store 50tons or more of CO₂, such as 100 tons or more of CO₂, including 150 tonsor more of CO₂, for instance 200 tons or more of CO₂, such as 250 tonsor more of CO₂, including 300 tons or more of CO₂, such as 350 tons ormore of CO₂, including 400 tons or more of CO₂, for instance 450 tons ormore of CO₂, such as 500 tons or more of CO₂, including 550 tons or moreof CO₂, such as 600 tons or more of CO₂, including 650 tons or more ofCO₂, for instance 700 tons or more of CO₂, for every 1000 tons of thecomposition. Thus, in some embodiments, the compositions of theinvention (e.g., precipitation material comprising carbonates,bicarbonates, or carbonates and bicarbonates) comprise 5% or more ofCO₂, such as 10% or more of CO₂, including 25% or more of CO₂, forinstance 50% or more of CO₂, such as 75% or more of CO₂, including 90%or more of CO₂. Such compositions, particularly precipitation materialof the invention may be used in the built environment. In someembodiments, the composition may be employed as a component of amanufactured item, such as a building material (e.g., component of acement, aggregate, concrete, or a combination thereof). The compositionremains a storage-stable CO₂-sequestering product, as use of thecomposition in a manufactured item (such as building material) does notresult in re-release of sequestered CO₂. In some embodiments,compositions of the invention (e.g., precipitation material comprisingcarbonates, bicarbonates, or carbonates and bicarbonates), when combinedwith Portland cement, may dissolve and combine with compounds of thePortland cement without releasing CO₂.

Conditions employed to convert CO₂ into carbonates, bicarbonates, orcarbonates and bicarbonates may convert one or more additional waste gasstream components into co-products (i.e., products produced from the oneor more additional components under CO₂-processing conditions), whereinsuch additional components include sulfur oxides (SOx); nitrogen oxides(NOx); carbon monoxide (CO); metals such as antimony (Sb), arsenic (As),barium (Ba), beryllium (Be), boron (B), cadmium (Cd), chromium (Cr),cobalt (Co), copper (Cu), lead (Pb), manganese (Mn), mercury (Hg),molybdenum (Mo), nickel (Ni), radium (Ra), selenium (Se), silver (Ag),strontium (Sr), thallium (Tl), vanadium (V), and zinc (Zn); particulatematter; halides or acid gases; organics; toxic substances; radioactiveisotopes, and the like. Co-products of such one or more additional wastegas stream components may, for the purpose of the invention, beconsidered derivatives of the one or more additional waste gas streamcomponents. Compositions of the invention may comprise carbonates,bicarbonates, or carbonates and bicarbonates in combination with one ormore additional waste gas stream components and/or co-products of one ormore additional waste gas stream components. In some embodiments, suchone or more additional components and/or co-products may be part of asolution comprising carbonates, bicarbonates, or carbonates andbicarbonates. In some embodiments, such one or more additionalcomponents and/or co-products may be part of precipitation material ofthe invention by precipitating the one or more additional componentsand/or co-products along with carbonates, bicarbonates, or carbonatesand bicarbonates, by trapping the one or more additional componentsand/or co-products in precipitation material comprising carbonates,bicarbonates, or carbonates and bicarbonates, or by some combinationthereof. In some embodiments, such one or more additional componentsand/or co-products may be part of a slurry comprising any combination ofthe foregoing solutions with precipitation material.

Compositions of the invention may comprise sulfates, sulfites, or thelike in addition to carbonate and/or bicarbonates. In some embodiments,compositions comprise 70-99.9% carbonates and/or bicarbonates along with0.05-30% sulfates and/or sulfites. For example, compositions maycomprise at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or99.9% carbonates and/or bicarbonates. Such compositions may furthercomprise at least 0.05%, 0.1%, 0.5%, 1.0%, 5.0%, 10%, 15%, 20%, 25%, or30% sulfates and/or sulfites. In some embodiments, compositions of theinvention comprise sulfur-based compounds of calcium, magnesium, orcombinations thereof, optionally precipitated or trapped inprecipitation material produced from waste gas streams comprising SOx(e.g., SO₂, SO₃, etc.). For example, magnesium and calcium may react toform MgSO₄ and CaSO₄, respectively, as well as other magnesium- andcalcium-containing compounds (e.g., sulfites), effectively removingsulfur from the waste gas stream (e.g., flue gas stream) without adesulfurization step such as flue gas desulfurization (“FGD”). Inaddition, compositions comprising CaSO₄, MgSO₄, and related compoundsmay be formed without additional release of CO₂. In instances where highlevels of sulfur-based compounds (e.g., sulfate) are present, theaqueous solution may be enriched with calcium and/or magnesium so thatcalcium and/or magnesium are available to form carbonate compoundsbefore, during, or after formation of CaSO₄, MgSO₄, and/or relatedcompounds. In some embodiments, multiple reaction products (e.g., MgCO₃,CaCO₃, CaSO₄, mixtures of the foregoing, and the like) are collected atdifferent stages, while in other embodiments a single reaction product(e.g., precipitation material comprising carbonates, sulfates, etc.) iscollected. FIG. 12A and FIG. 12B, for example, provide a comparison ofmorphologies between laboratory-synthesized magnesium carbonates withbrucite tailings (e.g., Mg(OH)₂) and synthetic flue gas (15% CO₂, 3.5%O₂, balance N₂) without SO₂ (FIG. 12A) and with 400 ppm SO₂ (FIG. 12B).The compositions of FIG. 12A and FIG. 12B represent a degree ofcarbonation of 30.9% and 31.1%, respectively.

Compositions of the invention may comprise nitrates, nitrites, and/orthe like. In some embodiments, compositions of the invention comprisesuch nitrogen-based compounds of calcium, magnesium, or combinationsthereof, optionally precipitated or trapped in precipitation materialproduced from waste gas streams comprising NOx (e.g., NO₂, NO₃, etc.).For example, magnesium and calcium may react to form Mg(NO₃)₂ andCa(NO₃)₂, respectively, as well as other magnesium- andcalcium-containing compounds (e.g., nitrates), effectively removingnitrogen from the waste gas stream (e.g., flue gas stream) without aselective catalytic reduction (“SCR”) step or non-selective catalyticreduction (“NSCR”) step. In addition, compositions comprising Ca(NO₃)₂,Mg(NO₃)₂, and related compounds may be formed without additional releaseof CO₂. Compositions of the invention may further comprise othercomponents, such as trace metals (e.g., mercury). Using mercury as anon-limiting example of a trace metal, compositions of the invention maycomprise elemental mercury (Hg), mercury salts comprising Hg²⁺ (e.g.,HgCl₂, HgCO₃, etc.), mercury salts comprising Hg⁺ (e.g., Hg₂Cl₂, Hg₂CO₃,etc.), mercury compounds comprising Hg²⁺ (e.g., HgO, organomercurycompounds, etc.), mercury compounds comprising Hg⁺ (e.g., Hg₂O,organomercury compounds, etc.), particulate mercury (Hg(p)), and thelike. Mercury salts comprising Hg²⁺, mercury salts comprising Hg⁺,mercury compounds comprising Hg²⁺, mercury compounds comprising Hg⁺, maybe considered mercury derivatives for the purpose of the invention. Insome embodiments, compositions of the invention comprise suchmercury-based compounds, optionally precipitated or trapped inprecipitation material produced from waste gas streams comprising tracemetals such as mercury. In some embodiments, compositions comprisemercury (or another metal) in a concentration of at least 0.1, 0.5, 1,5, 10, 50, 100, 500, 1,000, 5,000, 10,000 ppb. Mercury may react to formHgCO₃ or Hg₂CO₃ as well as other mercury-containing compounds (e.g.,chlorides, oxides), effectively removing mercury from the waste gasstream (e.g., flue gas stream) without a specific or non-specificmercury removal technology. In addition, compositions comprising mercuryand/or other trace metals may be formed without additional release ofCO₂.

Precipitation material of the invention may comprise several carbonatesand/or several carbonate mineral phases resulting from co-precipitation,wherein the precipitation material may comprise, for example, calciumcarbonate (e.g., calcite) together with magnesium carbonate (e.g.,nesquehonite). Precipitation material may also comprise a singlecarbonate in a single mineral phase including, but not limited to,calcium carbonate (e.g., calcite), magnesium carbonate (e.g.,nesquehonite), calcium magnesium carbonate (e.g., dolomite), or aferro-carbo-aluminosilicate. As different carbonates may be precipitatedin sequence, the precipitation material may be, depending upon theconditions under which it was obtained, relatively rich (e.g., 90% to95%) or substantially rich (e.g., 95%-99.9%) in one carbonate and/or onemineral phase, or the precipitation material may comprise an amount ofother carbonates and/or other mineral phase (or phases), wherein thedesired mineral phase is 50-90% of the precipitation material. It willbe appreciated that, in some embodiments, the precipitation material maycomprise one or more hydroxides (e.g., Ca(OH)₂, Mg(OH)₂) in addition tothe carbonates. It will also be appreciated that any of the carbonatesor hydroxides present in the precipitation material may be wholly orpartially amorphous. In some embodiments, the carbonates and/orhydroxides are wholly amorphous. It will also be appreciated that any ofthe carbonates or hydroxides present in the precipitation material maybe wholly or partially crystalline. In some embodiments, the carbonatesand/or hydroxides are wholly crystalline.

While many different carbonate-containing salts and compounds arepossible due to variability of starting materials, precipitationmaterial comprising magnesium carbonate, calcium carbonate, orcombinations thereof is particularly useful. Precipitation material maycomprise two or more different carbonate compounds, three or moredifferent carbonate compounds, four or more different carbonatecompounds, five or more different carbonate compounds, etc., includingnon-distinct, amorphous carbonate compounds. Precipitation material ofthe invention may comprise compounds having a molecular formulationX_(m)(CO₃)_(n), wherein X is any element or combination of elements thatcan chemically bond with a carbonate group or its multiple and m and nare stoichiometric positive integers. In some embodiments, X may be analkaline earth metal (elements found in column HA of the periodic tableof elements), an alkali metal (elements found in column IA of theperiodic table of elements), or some combination thereof. In someembodiments, the precipitation material comprises dolomite (CaMg(CO₃)₂),protodolomite, huntite (CaMg₃(CO₃)₄), and/or sergeevite(Ca₂Mg₁₁(CO₃)13.H₂O), which are carbonate minerals comprising bothcalcium and magnesium. In some embodiments, the precipitation materialcomprises calcium carbonate in one or more phases selected from calcite,aragonite, vaterite, or a combination thereof. In some embodiments, theprecipitation material comprises hydrated forms of calcium carbonate(e.g., Ca(CO₃).nH2O, wherein there are one or more structural waters inthe molecular formula) selected from ikaite (CaCO₃.6H₂O), amorphouscalcium carbonate (CaCO₃.nH₂O), monohydrocalcite (CaCO₃.H₂O), orcombinations thereof. In some embodiments, the precipitation materialcomprises magnesium carbonate, wherein the magnesium carbonate does nothave any waters of hydration. In some embodiments, the precipitationmaterial comprises magnesium carbonate, wherein the magnesium carbonatemay have any of a number of different waters of hydration (e.g.,Mg(CO₃).nH₂O) selected from 1, 2, 3, 4, or more than 4 waters ofhydration. In some embodiments, the precipitation material comprises 1,2, 3, 4, or more than 4 different magnesium carbonate phases, whereinthe magnesium carbonate phases differ in the number of waters ofhydration. For example, precipitation material may comprise magnesite(MgCO₃), barringtonite (MgCO₃.2H₂O), nesquehonite (MgCO₃.3H₂O),lansfordite (MgCO₃.5H₂O), and amorphous magnesium carbonate. In someembodiments, precipitation material comprises magnesium carbonates thatinclude hydroxide and waters of hydration such as artinite(MgCO₃.Mg(OH)₂.3H₂O), hydromagnesite (Mg₅(CO₃)₄(OH)₂.3H₂O), orcombinations thereof. As such, precipitation material may comprisecarbonates of calcium, magnesium, or combinations thereof in all or someof the various states of hydration listed herein. Precipitation rate mayalso influence the nature of the precipitation material with the mostrapid precipitation rate achieved by seeding the solution with a desiredphase. Without seeding, rapid precipitation may be achieved by, forexample, rapidly increasing the pH of the precipitation reactionmixture, which results in more amorphous constituents. Furthermore, thehigher the pH, the more rapid the precipitation, which precipitationresults in a more amorphous precipitation material.

In some embodiments, the amount by weight of calcium carbonate compoundsin the precipitation material may exceed the amount by weight ofmagnesium carbonate compounds in the precipitation material. In someembodiments, for example, the amount by weight of calcium carbonatecompounds in the precipitation material may exceed the amount by weightmagnesium carbonate compounds in the precipitation material by 5% ormore, such as 10% or more, 15% or more, 20% or more, 25% or more, 30% ormore. In some embodiments, the weight ratio of calcium carbonatecompounds to magnesium carbonate compounds in the precipitation materialranges from 1.5-5 to 1, such as 2-4 to 1, including 2-3 to 1. In someembodiments, the amount by weight of magnesium carbonate compounds inthe precipitation material may exceed the amount by weight of calciumcarbonate compounds in the precipitation material. For example, theamount by weight of magnesium carbonate compounds in the precipitationmaterial may exceed the amount by weight calcium carbonate compounds inthe precipitation material by 5% or more, such as 10% or more, 15% ormore, 20% or more, 25% or more, 30% or more. In some embodiments, theweight ratio of magnesium carbonate compounds to calcium carbonatecompounds in the precipitation material ranges from 1.5-5 to 1, such as2-4 to 1, including 2-3 to 1.

Precipitation material produced in certain divalent cation-containingaqueous solutions (e.g., seawater, brine, etc.) of the invention maycomprise carbonate compounds that, upon combination with fresh water,dissolve to produce a fresh water precipitation material comprisingcarbonate compounds that is more thermodynamically stable (in freshwater). As such, carbonate compounds of the initial precipitationmaterial may dissolve upon combination with fresh water to produce newcarbonate compounds and a new composition (e.g., precipitationmaterial). (CO₂ gas is not liberated in significant amounts, or in somecases, at all, in any such reaction.) The carbonate compounds of theinitial precipitation material may be compounds that are more stable insalt water than they are in fresh water, such that the carbonatecompounds of the initial precipitation material may be viewed asmetastable. The amount of carbonate compounds in precipitation material,as determined by coulometric titration, may be 40% or higher, such as70% or higher, including 80% or higher.

Adjusting major ion ratios during precipitation may influence the natureof the precipitation material. Major ion ratios have considerableinfluence on polymorph formation. For example, as the magnesium:calciumratio in the water increases, aragonite becomes the major polymorph ofcalcium carbonate in the precipitation material over low-magnesiumcalcite. At low magnesium:calcium ratios, low-magnesium calcite becomesthe major polymorph. In some embodiments, where Ca²⁺ and Mg²⁺ are bothpresent, the ratio of Ca²⁺ to Mg²⁺ (i.e., Ca²⁺:Mg²⁺) in theprecipitation material is between 1:1 and 1:2.5; 1:2.5 and 1:5; 1:5 and1:10; 1:10 and 1:25; 1:25 and 1:50; 1:50 and 1:100; 1:100 and 1:150;1:150 and 1:200; 1:200 and 1:250; 1:250 and 1:500; 1:500 and 1:1000, ora range thereof. For example, in some embodiments, the ratio of Ca²⁺ toMg²⁺ in the precipitation material is between 1:1 and 1:10; 1:5 and1:25; 1:10 and 1:50; 1:25 and 1:100; 1:50 and 1:500; or 1:100 and1:1000. In some embodiments, the ratio of Mg²⁺ to Ca²⁺ (i.e., Mg²⁺:Ca²⁺)in the precipitation material is between 1:1 and 1:2.5; 1:2.5 and 1:5;1:5 and 1:10; 1:10 and 1:25; 1:25 and 1:50; 1:50 and 1:100; 1:100 and1:150; 1:150 and 1:200; 1:200 and 1:250; 1:250 and 1:500; 1:500 and1:1000, or a range thereof. For example, in some embodiments, the ratioof Mg²⁺ to Ca²⁺ in the precipitation material is between 1:1 and 1:10;1:5 and 1:25; 1:10 and 1:50; 1:25 and 1:100; 1:50 and 1:500; or 1:100and 1:1000.

Due to variability of starting materials, carbonate-containing salts andcompounds comprising counterions other than calcium or magnesium arepossible. Such other counterions (e.g., As, Ag, Ba, Be, Cd, Co, Cr, Cu,Hg, Mo, Ni, Pb, Sb, Se, Sr, Tl, V, Zn etc.) may substitute for calciumand/or magnesium in carbonate-containing salts and compounds or occupyinterstitial spaces. In some embodiments, such other counterions,optionally as part of a salt or some other compound, may be encapsulatedby carbonate-containing salts and compounds. For example, in someembodiments, compositions of the invention (e.g., precipitationmaterial) comprise calcium carbonate in the form of aragonite. In suchembodiments, calcium may be replaced by a number of different metalsincluding, but not limited to strontium, lead, and zinc, each of which,in one form or another, may be found in one or more starting materials(e.g., waste gas stream, source of proton-removing agents, source ofdivalent cations, etc.) of the invention. Compositions may comprise, forexample, mossottite, which is aragonite rich in strontium, orcompositions may comprise a mixture of aragonite and strontianite (e.g.,(Ca,Sr)CO₃). Compositions may comprise, for example, tarnowitzite, whichis aragonite rich in lead, or compositions may comprise a mixture ofaragonite and cerussite (e.g., (Ca,Pb)CO₃). Compositions may comprise,for example, nicholsonite, which is aragonite rich in Zn, orcompositions may comprise a mixture of aragonite and smithsonite (e.g.,(Ca,Zn)CO₃). In view of the foregoing exemplary embodiments,compositions (e.g., precipitation material) may comprise carbonates,bicarbonates, or carbonates and bicarbonates of As, Ag, Ba, Be, Cd, Co,Cr, Cu, Hg, Mo, Ni, Pb, Sb, Se, Sr, Tl, V, or Zn. By way of example,compositions of the invention may comprise carbonates of Ag, Ba, Be, Cd,Co, Cu, Ni, Pb, Sr, Tl, Zn, or combinations thereof. Carbonates,bicarbonates, or carbonates and bicarbonates of the foregoing metals maybe independently formed (e.g., strontianite) or exist in a magnesiumand/or calcium matrix (e.g., mossottite). Metals such as As, Ag, Ba, Be,Cd, Co, Cr, Cu, Hg, Mo, Ni, Pb, Sb, Se, Sr, Tl, V, and Zn may beprovided by a waste gas stream, a source of proton-removing agents, asource of divalent cations, or a combination thereof. Metals and othercomponents found in such source (e.g., waste gas streams, sources ofproton-removing agents, sources of divalent cations) that do not formcarbonates, bicarbonates, or carbonates and bicarbonates may be trappedin or adsorbed on precipitation material. In some embodiments, metalsand/or other components form or become part of carbonates, bicarbonates,or carbonates and bicarbonates and become trapped in or adsorbed onprecipitation material after a metastable transition. For example,precipitation material of the invention may comprise aragonite rich instrontium. Such a composition, when produced from salt water, maydissolve in fresh water to produce precipitation material comprisingcalcite in which the strontium no longer substitutes for calcium.Instead, the strontium may become trapped in the precipitation materialor my be adsorbed onto the precipitation material. In some embodiments,the metals and/or other components form new compounds that becomeencapsulated in the precipitation material.

A composition of the invention (e.g., precipitation material or productsderived therefrom including supplementary cementitious materials,cement, fine aggregate, coarse aggregate, and combinations thereof suchas concrete) might contain, in one form or another, metals such as As,Ag, Ba, Be, Cd, Co, Cr, Cu, Hg, Mo, Ni, Pb, Se, Sb, Tl, V, or Zn, orcombinations thereof, as well as other chemical species that might beconsidered contaminants if released into the environment. Potential forrelease of such contaminants into the environment may be tested bymixing the composition with an extraction solution, agitating theresultant mixture, and filtering the agitated mixture to produce atestable leachate. Compositions of the invention may be tested using anyof a variety of tests as different tests have been developed to simulatedifferent environmental conditions. Such tests include, but are notlimited to, Toxicity Characteristic Leaching Procedure (TCLP; US EPAMethod 1311), Extraction Procedure Toxicity Test (EP-Tox; US EPA Method1310), Synthetic Precipitation Leaching Procedure (SPLP; US EPA Method1312), California Waste Extraction Test (WET; California Code ofRegulations), Soluble Threshold Limit Concentration (STLC; CaliforniaCode of Regulations), American Society for Testing and MaterialsExtraction Test (ASTM D 3987-85), and Multiple Extraction Procedure(MEP; US EPA Method 1320), as such tests and limits defined is suchtests exist on the filing date of this patent application. Regulatorywater extraction test conditions as defined by waste control regulationsin, for example, the United Kingdom, Thailand, Japan, Switzerland,Germany, Sweden, the Netherlands may also be used. Such tests may differin, for example, extraction solutions, liquid to solid (L/S) ratios,and/or number and duration of extractions. Regarding extract solutions,such tests commonly use aqueous acetic acid, aqueous citric acid,distilled water, synthetic rainwater, or carbonated water.

Tests for potential release of contaminants into the environment by acomposition of the invention may comprise modifying the chemical and/orphysical environment of the composition, such as modifying pH,temperature, pressure, time, and the like, in a repeatable manner toeffect a measurable release (e.g., in an extract or leachate) ofcontaminants the composition. In some embodiments, a composition may besubjected to a solution (e.g., aqueous solution) having a pH less thanpH 8.5, pH 8.0, pH 7.5, pH 7.0, pH 6.5, pH 6.0, pH 5.5, pH 5.2, pH 5.0,pH 4.8, pH 4.6, pH 4.4, pH 4.2, pH 4.0, pH 3.8, pH 3.6, pH 3.4, pH 3.2,pH 3.0, pH 2.8, pH 2.6, pH 2.4, pH 2.2, pH 2.0, pH 1.8, pH 1.6, pH 1.4,pH 1.2, pH 1.0, pH 0.8, pH 0.6, pH 0.4, or pH 0.2. Such pH levels may beobtained by adding acid (e.g., HCl) to water, or by preparing a bufferedsolution at a particular pH. As certain reagents commonly used toprepare acidic solutions or buffers may react with a composition of theinvention, proper selection of reagents is important to isolate theeffect of pH on the composition. For example, while phosphoric acid maybe used to prepare a buffered solution at a particular pH, phosphate mayreact with a composition comprising calcium carbonate such that calciumphosphate is formed. Tests for potential release of contaminants intothe environment may make use of a depressed or an elevated temperature.For example, in some embodiments, a temperature greater than 0° C., 10°C., 20° C., 25° C., 30° C., 40° C., 50° C., 60° C., 70° C., 80° C., 90°C., or 100° C. may be used. Temperatures in such tests may range betweenany of the foregoing (e.g., 60-80° C.; 20-25° C. (room temperature))temperature. The time during which a composition is subjected to aparticular pH and/or temperature may be any suitable time to effect ameasureable release of contaminants (if present). For example, in someembodiments, a composition may be subjected to a particular pH and/ortemperature for 0.5, 1, 2, 4, 6, 8, 16, 24, 32, 40, 48, 72, 96 hours.Time periods spanning from days (e.g., 5, 6, 7, etc), weeks (e.g., 1, 2,3, 4, etc.), or months (e.g., 2, 3, 4, 5, 6, etc.) are also within thescope of tests for potential release of contaminants into theenvironment. In some embodiments, for example, a test for potentialrelease of contaminants into the environment by a composition (e.g.,precipitation material or compositions comprising precipitation materialsuch as cement or concrete) of the invention consists essentially ofpreparing 2×1 L of an extraction fluid consisting essentially of anaqueous solution of acetic acid, wherein each 1 L of the extractionfluid consists essentially of 5.7 mL acetic acid in deionized water;grinding the composition such that particles of ground composition areless than 1 cm in the narrowest dimension if the particles are notalready less than 1 cm in the narrowest dimension; placing 100 g of theground composition into an extraction vessel with 2 L of the extractionfluid to produce an extraction composition; rotating the extractionvessel in an end-over-end fashion for 18±2 hours at room temperature;filtering the extraction composition through borosilicate glass fiberwith a pore size of 0.6 μm to 0.8 μm to produce a leachate; andadjusting pH of the leachate with 1N nitric acid to a pH of pH 2 or lessthan pH 2. Any suitable test or tests for detecting and quantifyingcontaminants, or lack thereof, in the leachate may be used. Theforegoing test is exemplary and those of skill in the art can designsimilar tests that may be used to effect detectable and quantifiablecontaminants, if such contaminants exist, from a composition of theinvention. It is to be understood that, in any of the tests forpotential release of contaminants into the environment, the addition ofadditional steps could affect potential release of contaminants into theenvironment and would necessitate comparison to the protocols set outherein to determine if adjusted levels of contaminants released due tothe additional steps is warranted.

Compositions of the invention (e.g., precipitation material or productsderived therefrom including supplementary cementitious materials,cement, fine aggregate, coarse aggregate, and combinations thereof suchas concrete) meet or improve upon limits for metals and/or otherchemical species defined in one or more of the foregoing tests (e.g.,TCLP) (as of the filing date of this application) such that compositionsof the invention are suitable for placement into the environment. Shoulda composition of the invention not meet or improve upon limits formetals and/or other chemical species as defined in one or more of theforegoing tests (e.g., TCLP), the composition may be effectively dilutedto produce a diluted composition that meets or exceed such limits. Insome embodiments, for example, precipitation material of the inventionmay, upon not meeting or improving upon a certain limit (e.g., 0.2 mg/Lin TCLP), be used for a supplementary cementitious material in cement.In such embodiments, the cement comprising the precipitation materialmay meet or improve upon the certain limit (e.g., 0.2 mg/L in TCLP) thatthe precipitation material alone did not meet or improve upon. As such,precipitation material of the invention may be used for supplementarycementitious materials, cement, fine aggregate, coarse aggregate,concrete, or combinations thereof, wherein one or more of theprecipitation material, supplementary cementitious materials, cement,fine aggregate, coarse aggregate, concrete, or combinations thereof meetor improve upon limits for metals and/or other chemical species definedin one or more of the foregoing tests (e.g., TCLP) (as of the filingdate of this application), and wherein such materials are suitable forplacement into the environment.

The Code of Federal Regulations (see 40 C.F.R. §261.24) contains a listof contaminants and their associated maximum allowable concentrations(as of the filing date of this application) in a TCLP extract from asolid or multiphasic material (e.g., slurry) such as a composition ofthe invention. If a contaminant (e.g., mercury) exceeds its maximumallowable concentration in a TCLP (Method 1311 in “Test Methods forEvaluating Solid Waste, Physical/Chemical Methods,” EPA PublicationSW-846, which is incorporated herein by reference in its entirety)extract of a material, then the material may be considered hazardous dueto the characteristic of toxicity. For instance, material containingcertain leachable heavy metals may be classified as hazardous materialif TCLP extracts have concentrations above threshold values for thoseheavy metals, which threshold values range from 0.2 mg/L (or ppm) for Hgand 100 mg/L for Ba. For example, if a TCLP analysis provides more than0.2 mg/L mercury in an extract, then the material may be classified ashazardous material with respect to mercury. Likewise, if a TCLP analysisprovides more than 100 mg/L barium in an extract, then the material maybe classified as hazardous material with respect to barium. The 40C.F.R. §261.24 includes, but is not limited to, As, Cd, Cr, Hg, and Pb,each of which might be found in waste gas streams resulting fromcombustion of fossil fuels (e.g., coal), and each of which, in one formor another, might be incorporated in compositions of the invention. Thelist also includes a number of contaminants that might be present inindustrial waste sources of divalent cations and/or proton-removingagents, which contaminants, in one form or another, might beincorporated in compositions of the invention. For example, fly ash,which may be a source of divalent cations and/or proton-removing agents,might contain As, Ba, Cd, Cr, Se, and/or Hg, each of which is found onthe list, and each of which, in one form or another, might beincorporated in compositions of the invention. In another non-limitingexample, red mud, which may be a source of divalent cations and/orproton-removing agents, might contain Cr, Ba, Pb, and/or Zn, each ofwhich is found on the list in 40 C.F.R. §261.24, and each of which, inone form or another, might be incorporated in compositions of theinvention.

As such, in some embodiments, a composition of the invention comprisescontaminants predicted not to leach into the environment by one or moretests selected from the group consisting of Toxicity CharacteristicLeaching Procedure, Extraction Procedure Toxicity Test, SyntheticPrecipitation Leaching Procedure, California Waste Extraction Test,Soluble Threshold Limit Concentration, American Society for Testing andMaterials Extraction Test, and Multiple Extraction Procedure. Tests andcombinations of tests may be chosen depending upon likely contaminantsand storage conditions of the composition. For example, in someembodiments, the composition may comprise As, Cd, Cr, Hg, and Pb (orproducts thereof), each of which might be found in a waste gas stream ofa coal-fired power plant. Since TCLP tests for As, Ba, Cd, Cr, Pb, Hg,Se, and Ag, TCLP may be an appropriate test for solid and multiphasiccompositions stored in the environment (e.g., built environment). Insome embodiments, a composition of the invention comprises As, whereinthe composition is predicted not to leach As into the environment. Forexample, a TCLP extract of the composition may provide less than 5.0mg/L As indicating that the composition is not hazardous with respect toAs. In some embodiments, a composition of the invention comprises Cd,wherein the composition is predicted not to leach Cd into theenvironment. For example, a TCLP extract of the composition may provideless than 1.0 mg/L Cd indicating that the composition is not hazardouswith respect to Cd. In some embodiments, a composition of the inventioncomprises Cr, wherein the composition is predicted not to leach Cr intothe environment. For example, a TCLP extract of the composition mayprovide less than 5.0 mg/L Cr indicating that the composition is nothazardous with respect to Cr. In some embodiments, a composition of theinvention comprises Hg, wherein the composition is predicted not toleach Hg into the environment. For example, a TCLP extract of thecomposition may provide less than 0.2 mg/L Hg indicating that thecomposition is not hazardous with respect to Hg. In some embodiments, acomposition of the invention comprises Pb, wherein the composition ispredicted not to leach Pb into the environment. For example, a TCLPextract of the composition may provide less than 5.0 mg/L Pb indicatingthat the composition is not hazardous with respect to Pb. In someembodiments, a composition of the invention may be non-hazardous withrespect to a combination of different contaminants in a given test. Forexample, the composition may be non-hazardous with respect to all metalcontaminants in a given test. A TCLP extract of a composition, forinstance, may be less than 5.0 mg/L in As, 100.0 mg/L in Ba, 1.0 mg/L inCd, 5.0 mg/mL in Cr, 5.0 mg/L in Pb, 0.2 mg/L in Hg, 1.0 mg/L in Se, and5.0 mg/L in Ag. Indeed, a majority if not all of the metals tested in aTCLP analysis on a composition of the invention may be below detectionlimits. In some embodiments, a composition of the invention may benon-hazardous with respect to all (e.g., inorganic, organic, etc.)contaminants in a given test. In some embodiments, a composition of theinvention may be non-hazardous with respect to all contaminants in anycombination of tests selected from the group consisting of ToxicityCharacteristic Leaching Procedure, Extraction Procedure Toxicity Test,Synthetic Precipitation Leaching Procedure, California Waste ExtractionTest, Soluble Threshold Limit Concentration, American Society forTesting and Materials Extraction Test, and Multiple ExtractionProcedure. As such, compositions of the invention may effectivelysequester CO₂ (e.g., as carbonates, bicarbonates, or a combinationsthereof) along with various chemical species (or co-products thereof)from waste gas streams, industrial waste sources of divalent cations,industrial waste sources of proton-removing agents, or combinationsthereof that might be considered contaminants if released into theenvironment. Compositions of the invention incorporate environmentalcontaminants (e.g., metals and co-products of metals such as Hg, Ag, As,Ba, Be, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Sb, Se, Tl, V, Zn, orcombinations thereof) in a non-leachable form.

In some embodiments, the invention provides a method of treating a wastegas stream comprising carbon dioxide and, optionally, any of a number ofsolid, liquid, or multiphasic waste streams, to produce a compositionthat provides a leachate in compliance with the TCLP protocol. Suchcompositions of the invention may include precipitation material,supplementary cementitious materials, cement, fine aggregate, coarseaggregate, concrete, or combinations thereof, each of which may betested in accordance with Example 2 or Example 3 below. In someembodiments, for example, precipitation material, supplementarycementitious materials, cement, fine aggregate, coarse aggregate,concrete, or combinations thereof may be tested in a TCLP procedureconsisting of preparing 2×1 L of an extraction fluid consistingessentially of an aqueous solution of acetic acid, wherein each 1 L ofthe extraction fluid consists essentially of 5.7 mL acetic acid indeionized water; grinding the solid such that particles of ground solidare less than 1 cm in the narrowest dimension if the particles are notalready less than 1 cm in the narrowest dimension; placing 100 g of theground solid into an extraction vessel with 2 L of the extraction fluidto produce an extraction composition; rotating the extraction vessel inan end-over-end fashion for 18±2 hours at room temperature; filteringthe extraction composition through borosilicate glass fiber with a poresize of 0.6 μm to 0.8 μm to produce a leachate; adjusting pH of theleachate with 1N nitric acid to a pH of pH 2 or less than pH 2, andanalyzing the leachate for metals and/or other chemical species. In someembodiments, a composition of the invention provides less than 0.05mg/L, 0.50 mg/L, 5.0 mg/L, 50 mg/L, or 500 mg/L As in the leachateprovided by the TCLP procedure. Alternatively, or in combination withthe foregoing embodiment, the composition provides less than 1.00 mg/L,10.0 mg/L, 100 mg/L, 1,000 mg/L, or 10,000 mg/L Ba in the leachateprovided by the TCLP procedure. Alternatively, or in combination withany of the foregoing embodiments, the composition provides less than0.01 mg/L, 0.10 mg/L, 1.0 mg/L, 10 mg/L, or 100 mg/L Cd in the leachateprovided by the TCLP procedure. Alternatively, or in combination withany of the foregoing embodiments, the composition provides less than0.05 mg/L, 0.50 mg/L, 5.0 mg/L, 50 mg/L, or 500 mg/L Pb in the leachateprovided by the TCLP procedure. Alternatively, or in combination withany of the foregoing embodiments, the composition provides less than0.002 mg/L, 0.02 mg/L, 0.20 mg/L, 2.0 mg/L, or 20 mg/L Hg in theleachate provided by the TCLP procedure. Alternatively, or incombination with any of the foregoing embodiments, the compositionprovides less than 0.01 mg/L, 0.10 mg/L, 1.0 mg/L, 10 mg/L, or 100 mg/LSe in the leachate provided by the TCLP procedure. Alternatively, or incombination with any of the foregoing embodiments, the compositionprovides less than 0.05 mg/L, 0.50 mg/L, 5.0 mg/L, 50 mg/L, or 500 mg/LAg in the leachate provided by the TCLP procedure. In view of theforgoing, and by way of example only, the composition provides less than0.2 mg/L Hg and less than 1.0 mg/L cadmium in the leachate provided bythe TCLP procedure. It should be understood that the foregoing areexemplary and that any combination of metals and levels of metals in theleachate as described herein is within the scope of the invention. Suchcompositions of the invention, as described herein, are suitable forbuilding products and the like.

Precipitation material, which comprises one or more synthetic carbonatesderived from industrial CO₂, reflects the relative carbon isotopecomposition (δ¹³C) of the fossil fuel (e.g., coal, oil, natural gas, orflue gas) from which the industrial CO₂ (from combustion of the fossilfuel) was derived. The relative carbon isotope composition (δ¹³C) valuewith units of ‰ (per mille) is a measure of the ratio of theconcentration of two stable isotopes of carbon, namely ¹²C and ¹³C,relative to a standard of fossilized belemnite (the PDB standard).

δ¹³C‰=[(¹³C/¹²C sample−¹³C/¹²C PDB standard)/(¹³C/¹²C PDBstandard)]×1000

As such, the δ¹³C value of the synthetic carbonate-containingprecipitation material serves as a fingerprint for a CO₂ gas source. Theδ¹³C value may vary from source to source (i.e., fossil fuel source),but the δ¹³C value for composition of the invention generally, but notnecessarily, ranges between −9‰ to −35‰. In some embodiments, the δ¹³Cvalue for the synthetic carbonate-containing precipitation material isbetween −1‰ and −50‰, between −5‰ and −40‰, between −5‰ and −35‰,between −7‰ and −40‰, between −7‰ and −35‰, between −9‰ and −40‰, orbetween −9‰ and −35‰. In some embodiments, the δ¹³C value for thesynthetic carbonate-containing precipitation material is less than(i.e., more negative than) −3‰, −5‰, −6‰, −7‰, −8‰, −9‰, −10‰, −11‰,−12‰, −13‰, −14‰, −15‰, −16‰, −17‰, −18‰, −19‰, −20‰, −21‰, −22‰, −23‰,−24‰, −25‰, −26‰, −27‰, −28‰, −29‰, −30‰, −31‰, −32‰, −33‰, −34‰, −35‰,−36‰, −37‰, −38‰, −39‰, −40‰, −41‰, −42‰, −43‰, −44‰, or −45‰, whereinthe more negative the δ¹³C value, the more rich the syntheticcarbonate-containing composition is in 12C. Any suitable method may beused for measuring the δ¹³C value, methods including, but no limited to,mass spectrometry or off-axis integrated-cavity output spectroscopy(off-axis ICOS).

In addition to magnesium- and calcium-containing products of theprecipitation reaction, compounds and materials comprising silicon,aluminum, iron, and others may also be prepared and incorporated withinprecipitation material with methods and systems of the invention.Incorporation of such compounds in precipitation material may be desiredto alter the reactivity of cements comprising the precipitation materialresulting from the process, or to change the properties of cured cementsand concretes made from them. Incorporation of one or more componentssuch as amorphous silica, amorphous aluminosilicates, crystallinesilica, calcium silicates, calcium alumina silicates, etc. may enhancethe ability of precipitation material of the invention to retainCO₂-processing co-products (e.g., sulfates; sulfites; metals describedherein and their salts and other compounds, etc.). Retaining theCO₂-processing co-products may comprise encapsulation or integration(e.g., chemical bonding of the CO₂-processing co-products to variousspecies in the precipitation material). Material comprising metalsilicates may be added to the precipitation reaction mixture as onesource of these components, to produce carbonate-containingprecipitation material which contains one or more components, such asamorphous silica, amorphous aluminosilicates, crystalline silica,calcium silicates, calcium alumina silicates, etc. In some embodiments,the precipitation material comprises carbonates (e.g., calciumcarbonate, magnesium carbonate) and silica in a carbonate:silica ratiobetween 1:1 and 1:1.5; 1:1.5 and 1:2; 1:2 and 1:2.5; 1:2.5 and 1:3; 1:3and 1:3.5; 1:3.5 and 1:4; 1:4 and 1:4.5; 1:4.5 and 1:5; 1:5 and 1:7.5;1:7.5 and 1:10; 1:10 and 1:15; 1:15 and 1:20, or a range thereof. Forexample, in some embodiments, the precipitation material comprisescarbonates and silica in a carbonate:silica ratio between 1:1 and 1:5,1:5 and 1:10, or 1:5 and 1:20. In some embodiments, the precipitationmaterial comprises silica and carbonates (e.g., calcium carbonate,magnesium carbonate) in a silica:carbonate ratio between 1:1 and 1:1.5;1:1.5 and 1:2; 1:2 and 1:2.5; 1:2.5 and 1:3; 1:3 and 1:3.5; 1:3.5 and1:4; 1:4 and 1:4.5; 1:4.5 and 1:5; 1:5 and 1:7.5; 1:7.5 and 1:10; 1:10and 1:15; 1:15 and 1:20, or a range thereof. For example, in someembodiments, the precipitation material comprises silica and carbonatesin a silica:carbonate ratio between 1:1 and 1:5, 1:5 and 1:10, or 1:5and 1:20. In general, precipitation material produced by methods of theinvention comprises mixtures of silicon-based material and at least onecarbonate phase. In general, the more rapid the reaction rate, the moresilica is incorporated with the carbonate-containing precipitationmaterial, provided silica is present in the precipitation reactionmixture (i.e., provided silica was not removed after digestion ofmaterial comprising metal silicates).

Precipitation material may be in a storage-stable form (which may simplybe air-dried precipitation material), and may be stored above groundunder exposed conditions (i.e., open to the atmosphere) withoutsignificant, if any, degradation (e.g., loss of CO₂) for extendeddurations. In some embodiments, the precipitation material may be stableunder exposed conditions for 1 year or longer, 5 years or longer, 10years or longer, 25 years or longer, 50 years or longer, 100 years orlonger, 250 years or longer, 1000 years or longer, 10,000 years orlonger, 1,000,000 years or longer, or even 100,000,000 years or longer.A storage-stable form of the precipitation material may be stable undera variety of different environment conditions, for example, fromtemperatures ranging from −100° C. to 600° C. and humidity ranging from0 to 100%, where the conditions may be calm, windy, or stormy. As thestorage-stable form of the precipitation material undergoes little ifany degradation while stored above ground under normal rainwater pH, theamount of degradation, if any, as measured in terms of CO₂ gas releasefrom the product, does not exceed 5% per year, and in certainembodiments will not exceed 1% per year or 0.001% per year. Indeed,precipitation material provided by the invention does not release morethan 1%, 5%, or 10% of its total CO₂ when exposed to normal conditionsof temperature and moisture, including rainfall of normal pH for atleast 1, 2, 5, 10, or 20 years, or for more than 20 years, for example,for more than 100 years. In some embodiments, the precipitation materialdoes not release more than 1% of its total CO₂ when exposed to normalconditions of temperature and moisture, including rainfall of normal pHfor at least 1 year. In some embodiments, the precipitation materialdoes not release more than 5% of its total CO₂ when exposed to normalconditions of temperature and moisture, including rainfall of normal pHfor at least 1 year. In some embodiments, the precipitation materialdoes not release more than 10% of its total CO₂ when exposed to normalconditions of temperature and moisture, including rainfall of normal pHfor at least 1 year. In some embodiments, the precipitation materialdoes not release more than 1% of its total CO₂ when exposed to normalconditions of temperature and moisture, including rainfall of normal pHfor at least 10 years. In some embodiments, the precipitation materialdoes not release more than 1% of its total CO₂ when exposed to normalconditions of temperature and moisture including rainfall of normal pHfor at least 100 years. In some embodiments, the precipitation materialdoes not release more than 1% of its total CO₂ when exposed to normalconditions of temperature and moisture, including rainfall of normal pHfor at least 1000 years.

Any suitable surrogate marker or test that is reasonably able to predictsuch stability may be used. For example, an accelerated test comprisingconditions of elevated temperature and/or moderate to more extreme pHconditions is reasonably able to indicate stability over extendedperiods of time. For example, depending on the intended use andenvironment of the precipitation material, a sample of the precipitationmaterial may be exposed to 50, 75, 90, 100, 120, or 150° C. for 1, 2, 5,25, 50, 100, 200, or 500 days at between 10% and 50% relative humidity,and a loss less than 1%, 2%, 3%, 4%, 5%, 10%, 20%, 30%, or 50% of itscarbon may be considered sufficient evidence of stability ofprecipitation material of the invention for a given period (e.g., 1, 10,100, 1000, or more than 1000 years).

Any of a number of suitable methods may be used to test the stability ofthe precipitation material including physical test methods and chemicaltest methods, wherein the methods are suitable for determining that thecompounds in the precipitation material are similar to or the same asnaturally occurring compounds known to have the above specifiedstability (e.g., limestone). CO₂ content of the precipitation materialmay be monitored by any suitable method, one such non-limiting examplebeing coulometry. Other conditions may be adjusted as appropriate,including pH, pressure, UV radiation, and the like, again depending onthe intended or likely environment. It will be appreciated that anysuitable conditions may be used that one of skill in the art wouldreasonably conclude indicate the requisite stability over the indicatedtime period. In addition, if accepted chemical knowledge indicates thatthe precipitation material would have the requisite stability for theindicated period this may be used as well, in addition to or in place ofactual measurements. For example, some carbonate compounds that may bepart of a precipitation material of the invention (e.g., in a givenpolymorphic form) may be well-known geologically and known to havewithstood normal weather for decades, centuries, or even millennia,without appreciable breakdown, and so have the requisite stability.

Exemplary carbon dioxide release protocols for a composition of theinvention may comprise modifying the chemical and/or physicalenvironment of the composition, such as modifying pH, temperature,pressure, time, and the like, in a repeatable manner to effect ameasurable release of carbon dioxide from the composition. In someembodiments, a composition may be subjected to a solution (e.g., aqueoussolution) having a pH less than pH 8.5, pH 8.0, pH 7.5, pH 7.0, pH 6.5,pH 6.0, pH 5.5, pH 5.2, pH 5.0, pH 4.8, pH 4.6, pH 4.4, pH 4.2, pH 4.0,pH 3.8, pH 3.6, pH 3.4, pH 3.2, pH 3.0, pH 2.8, pH 2.6, pH 2.4, pH 2.2,pH 2.0, pH 1.8, pH 1.6, pH 1.4, pH 1.2, pH 1.0, pH 0.8, pH 0.6, pH 0.4,or pH 0.2. Such pH levels may be obtained by adding acid (e.g., HCl) towater, or by preparing a buffered solution at a particular pH. Ascertain reagents commonly used to prepare acidic solutions or buffersmay react with a composition of the invention, proper selection ofreagents is important to isolate the effect of pH on the composition.For example, while phosphoric acid may be used to prepare a bufferedsolution at a particular pH, phosphate may react with a compositioncomprising calcium carbonate such that calcium phosphate is formed. Withthis in mind, additional chemical agents should not be added that mayeither promote release of carbon dioxide by a reaction other than anacid-base reaction or react with the composition to form a differentcomposition. A carbon dioxide release protocol for a composition of theinvention may make use of a depressed or an elevated temperature. Forexample, in some embodiments, a temperature greater than 0° C., 10° C.,20° C., 25° C., 30° C., 40° C., 50° C., 60° C., 70° C., 80° C., 90° C.,or 100° C. may be used. Temperatures in such tests may range between anyof the foregoing (e.g., 60-80° C., 20-25° C. (room temperature)). Thetime during which the composition is subjected to a particular pH and/ortemperature may be for any suitable time to effect release of carbondioxide. For example, in some embodiments, a composition may besubjected to a particular pH and/or temperature for 0.5, 1, 2, 4, 6, 8,16, 24, 32, 40, 48, 72, 96 hours. Time periods spanning from days (e.g.,5, 6, 7, etc), weeks (e.g., 1, 2, 3, 4, etc.), or months (e.g., 2, 3, 4,5, 6, etc.) are also within the scope of carbon dioxide releaseprotocols of the invention. In some embodiments, for example, acomposition may be tested in a carbon dioxide release protocolconsisting essentially of grinding the composition of the invention(e.g., precipitation material or compositions comprising precipitationmaterial such as cement or concrete) such that particles of groundcomposition are less than 1 cm in the narrowest dimension if theparticles are not already less than 1 cm in the narrowest dimension andimmersing the ground composition in a solution having a pH between pH4.8 and pH 5.2 and a temperature between 60 and 80° C. for 48 hours. Insome embodiments, the composition produces no more than 0.25, 0.5, 1.0,2.0, 4.0, 6.0, 8.0, 10, 20, 30, 40, or 50 grams of carbon dioxide per100 g of the composition. Any suitable test or tests for detecting andquantifying the release of carbon dioxide, or lack thereof may be used.This test is exemplary and those of skill in the art can design similartests which may be used to effect a measureable release of carbondioxide from a composition. It is to be understood that in any of thecarbon dioxide release protocols, the addition of additional steps couldaffect CO₂ release and would necessitate comparison to the protocols setout herein to determine if adjusted levels of CO₂ release due to theadditional steps is warranted.

The carbonate-containing precipitation material, which serves tosequester CO₂ in a form that is stable over extended periods of time(e.g., geologic time scales), may be stored for extended durations, asdescribed above. The precipitation material, if needed to achieve acertain ratio of carbonates to silica, may also be mixed withsilicon-based material (e.g., from separated silicon-based materialafter material comprising metal silicates digestion; commerciallyavailable SiO₂; etc.) to form pozzolanic material. Pozzolanic materialsof the invention are siliceous or aluminosiliceous materials which, whencombined with an alkali such as calcium hydroxide (Ca(OH)₂), exhibitcementitious properties by forming calcium silicates and othercementitious materials. SiO₂-containing materials such as volcanic ash,fly ash, silica fume, high reactivity metakaolin, and ground granulatedblast furnace slag, and the like may be used to fortify compositions ofthe invention producing pozzolanic materials. In some embodiments,pozzolanic materials of the invention are fortified with 0.5% to 1.0%,1.0% to 2.0%; 2.0% to 4.0%, 4.0% to 6.0%, 6.0% to 8.0%, 8.0% to 10.0%,10.0% to 15.0%, 15.0% to 20.0%, 20.0% to 30.0%, 30.0% to 40.0%, 40.0% to50.0%, or an overlapping range thereof, an SiO₂-containing material.Such SiO₂-containing material may be obtained from, for example, anelectrostatic precipitator or fabric filter of the invention.

As indicated above, in some embodiments, precipitation materialcomprises metastable carbonate compounds characterized in that suchcarbonates are more stable in salt water than in fresh water, such thatupon contact with fresh water of any pH the carbonates dissolve andre-precipitate into other fresh water-stable minerals. In someembodiments, the carbonate compounds may be present as small particles,for example, with particle sizes ranging from 0.1 μm to 100 μm, 1 to 100μm, 10 to 100 μm, 50 to 100 μm as determined by scanning electronmicroscopy (SEM). In some embodiments, particle sizes of the carbonatecompounds range from 0.5 to 10 μm as determined by SEM. In someembodiments, the particle sizes exhibit a single modal distribution. Insome embodiments, the particle sizes exhibit a bimodal or multi-modaldistribution. In certain embodiments, the particles have a high surfaceare ranging from, for example, 0.5 to 100 m²/gm, 0.5 to 50 m²/gm, or 0.5to 2.0 m²/gm as determined by Brauner, Emmit, & Teller (BET) SurfaceArea Analysis. In some embodiments, precipitation material may compriserod-shaped crystals and/or amorphous solids. The rod-shaped crystals mayvary in structure, and in certain embodiments have a length to diameterratio ranging from 500 to 1, 250 to 1, or 10 to 1. In certainembodiments, the length of the crystals ranges from 0.5 μm to 500 μm, 1μm to 250 μm, or 5 μm to 100 μm. In yet other embodiments, substantiallycompletely amorphous solids are produced.

Spray-dried material (e.g., precipitation material, silicon-basedmaterial, pozzolanic material, etc.), by virtue of being spray dried,may have a consistent particle size (i.e., the spray-dried material mayhave a relatively narrow particle size distribution). As such, in someembodiments, at least 50%, 60%, 70%, 80%, 90%, 95%, 97%, or 99% of thespray-dried material falls within ±10 microns, ±20 microns, ±30 microns,±40 microns, ±50 microns, ±75 microns, ±100 microns, or ±250 microns ofa given mean particle diameter. In some embodiments, the given meanparticle diameter is between 5 and 500 microns. In some embodiments, thegiven mean particle is between 5 and 250 microns. In some embodiments,the given mean particle diameter is between 5 and 100 microns. In someembodiments, the given mean particle diameter is between 5 and 50microns. In some embodiments, the given mean particle diameter isbetween 5 and 25 microns. For example, in some embodiments, at least 70%of the spray-dried material falls within ±50 microns of a given meanparticle diameter, wherein the given mean particle diameter is between 5and 500 microns, such as between 50 and 250 microns, or between 100 and200 microns. Such spray-dried material may be used to manufacturecement, fine aggregate, mortar, coarse aggregate, concrete, and/orpozzolans of the invention; however, one of skill in the art willrecognize that manufacture of cement, fine aggregate, mortar, coarseaggregate, concrete, and/or pozzolans does not require spray-driedprecipitation material. Air-dried precipitation material, for example,may also be used to manufacture cement, fine aggregate, mortar, coarseaggregate, concrete, and/or pozzolans of the invention.

Generally, pozzolanic material has lower cementitious properties thanordinary Portland cement, but in the presence of a lime-rich media likecalcium hydroxide, it shows better cementitious properties towards laterday strength (>28 days). The pozzolanic reaction may be slower than therest of the reactions which occur during cement hydration, and thus theshort-term strength of concretes that include pozzolanic material of theinvention may not be as high as concrete made with purely cementitiousmaterials. The mechanism for this display of strength is the reaction ofsilicates with lime to form secondary cementitious phases (calciumsilicate hydrates with a lower C/S ratio), which display gradualstrengthening properties usually after 7 days. The extent of thestrength development ultimately depends upon the chemical composition ofthe pozzolanic material. Increasing the composition of silicon-basedmaterial (optionally with added silica and/or alumina), especiallyamorphous silicon-based material, generally produces better pozzolanicreactions and strengths. Highly reactive pozzolans, such as silica fumeand high reactivity metakaolin may produce “high early strength”concrete that increases the rate at which concrete comprisingprecipitation material of the invention gains strength.

Precipitation material comprising silicates and aluminosilicates may bereadily employed in the cement and concrete industry as pozzolanicmaterial by virtue of the presence of the finely divided siliceousand/or alumino-siliceous material (e.g., silicon-based material). Thesiliceous and/or aluminosiliceous precipitation material may be blendedwith Portland cement, or added as a direct mineral admixture in aconcrete mixture. In some embodiments, pozzolanic material comprisescalcium and magnesium in a ratio (as above) that perfects setting time,stiffening, and long-term stability of resultant hydration products(e.g., concrete). Crystallinity of carbonates, concentration ofchlorides, sulfates, alkalis, etc. in the precipitation material may becontrolled to better interact with Portland cement. In some embodiments,precipitation material comprises silica in which 10-20%, 20-30%, 30-40%,40-50%, 50-60%, 60-70%, 70-80%, 80-90%, 90-95%, 95-98%, 98-99%, 99-99.9%of the silica has a particle size less than 45 microns (e.g., in thelongest dimension). In some embodiments, siliceous precipitationmaterial comprises aluminosilica in which 10-20%, 20-30%, 30-40%,40-50%, 50-60%, 60-70%, 70-80%, 80-90%, 90-95%, 95-98%, 98-99%, 99-99.9%of the aluminosilica has a particle size less than 45 microns. In someembodiments, siliceous precipitation material comprises a mixture ofsilica and aluminosilica in which 10-20%, 20-30%, 30-40%, 40-50%,50-60%, 60-70%, 70-80%, 80-90%, 90-95%, 95-98%, 98-99%, 99-99.9% of themixture has a particle size less than 45 microns (e.g., in the biggestdimension).

Pozzolanic material produced by the methods disclosed herein may beemployed as a construction material, which material may be processed foruse as a construction material or processed for use in an existingconstruction material for buildings (e.g., commercial, residential,etc.) and/or infrastructure (e.g., pavements, roads, bridges,overpasses, walls, levees, dams, etc.). The construction material may beincorporated into any structure, the structures further includingfoundations, parking structures, houses, office buildings, commercialoffices, governmental buildings, and support structures (e.g., footingsfor gates, fences and poles) is considered a part of the builtenvironment. The construction material may be a constituent of astructural or nonstructural component of such structure. An additionalbenefit of using pozzolanic material as a construction material or in aconstruction material is that CO₂ employed in the process (e.g., CO₂obtained from a waste gas stream) is effectively sequestered in thebuilt environment.

In some embodiments, pozzolanic material of the invention may beemployed as a component of a hydraulic cement (e.g., ordinary Portlandcement), which sets and hardens after combining with water. Setting andhardening of the product produced by combining the precipitationmaterial with cement and water results from the production of hydratesthat are formed from the cement upon reaction with water, wherein thehydrates are essentially insoluble in water. Such hydraulic cements,methods for their manufacture and use are described in co-pending U.S.patent application Ser. No. 12/126,776, filed on 23 May 2008, thedisclosure of which application is incorporated herein by reference. Insome embodiments, pozzolanic material blended with cement is between0.5% and 1.0%, 1.0% and 2.0%, 2.0% and 4.0%, 4.0% and 6.0%, 6.0% and8.0%, 8.0% and 10.0%, 10.0% and 15.0%, 15.0% and 20.0%, 20.0% and 30.0%,30.0% and 40.0%, 40.0% and 50.0%, 50% and 60%, or a range thereof,pozzolanic material by weight. For example, in some embodiments,pozzolanic material blended with cement is between 0.5% and 2.0%, 1.0%and 4.0%, 2.0% and 8.0%, 4.0% and 15.0%, 8.0% and 30.0%, or 15.0% and60.0% pozzolanic material by weight.

In some embodiments, pozzolanic material is blended with othercementitious materials or mixed into cements as an admixture oraggregate. Mortars of the invention find use in binding constructionblocks (e.g., bricks) together and filling gaps between constructionblocks. Mortars of the invention may also be used to fix existingstructure (e.g., to replace sections where the original mortar hasbecome compromised or eroded), among other uses.

In some embodiments, the pozzolanic material may be utilized to produceaggregates. In some embodiments, aggregate is produced from theprecipitation material by pressing and subsequent crushing. In someembodiments, aggregate is produced from the precipitation material byextrusion and breaking resultant extruded material. Such aggregates,methods for their manufacture and use are described in co-pending U.S.patent application Ser. No. 12/475,378, filed on 29 May 2009, thedisclosure of which is incorporated herein by reference in it entirety.

The following examples are put forth so as to provide those of ordinaryskill in the art with a complete disclosure and description of how tomake and use the invention, and are not intended to limit the scope ofthe invention. Efforts have been made to ensure accuracy with respect tonumbers used (e.g. amounts, temperature, etc.), but some experimentalerrors and deviations should be accounted for. Unless indicatedotherwise, parts are parts by weight, molecular weight is weight averagemolecular weight, temperature is in degrees Centigrade (° C.), andpressure is at or near atmospheric.

EXAMPLES

The following analytical instrumentation and methods of use thereof maybe used to characterize materials produced in accordance with theinvention.

Coulometry: Liquid and solid carbon containing samples are acidifiedwith 2.0 N perchloric acid (HClO₄) to evolve carbon dioxide gas into acarrier gas stream, and subsequently scrubbed with 3% w/v silver nitrateat pH 3.0 to remove any evolved sulfur gasses prior to analysis by aninorganic carbon coulometer (UIC Inc, model CM5015). Samples of cement,fly ash, and seawater are heated after addition of perchloric acid witha heated block to aid digestion of the sample.

Brunauer-Emmett-Teller (“BET”) Specific Surface Area: Specific surfacearea (SSA) measurement is by surface absorption with dinitrogen (BETmethod). SSA of dry samples is measured with a Micromeritics Tristar™ II3020 Specific Surface Area and Porosity Analyzer after preparing thesample with a Flowprep™ 060 sample degas system. Briefly, samplepreparation involves degassing approximately 1.0 g of dry sample at anelevated temperature while exposing to a stream of dinitrogen gas toremove residual water vapor and other adsorbants from the samplesurfaces. The purge gas in the sample holder is subsequently evacuatedand the sample cooled before being exposed to dinitrogen gas at a seriesof increasing pressures (related to adsorption film thickness). Afterthe surface is blanketed, the dinitrogen is released from the surface ofthe particles by systematic reduction of the pressure in the sampleholder. The desorbed gas is measured and translated to a total surfacearea measurement.

Particle Size Analysis (“PSA”): Particle size analysis and distributionis measured using static light scattering. Dry particles are suspendedin isopropyl alcohol and analyzed using a Horiba Particle SizeDistribution Analyzer (Model LA-950V2) in dual wavelength/laserconfiguration. Mie scattering theory is used to calculate the populationof particles as a function of size fraction, from 0.1 mm to 1000 mm.

Powder X-ray Diffraction (“XRD”): Powder X-ray diffraction is undertakenwith a Rigaku Miniflex™ (Rigaku) to identify crystalline phases andestimate mass fraction of different identifiable sample phases. Dry,solid samples are hand-ground to a fine powder and loaded on sampleholders. The X-ray source is a copper anode (Cu kα), powered at 30 kVand 15 mA. The X-ray scan is run over 5-90°2θ, at a scan rate of 2°2θper min, and a step size of 0.01°2θ per step. The X-ray diffractionprofile is analyzed by Rietveld refinement using the X-ray diffractionpattern analysis software Jade™ (version 9, Materials Data Inc. (MDI)).

Fourier Transform Infrared (“FT-IR”) spectroscopy: FT-IR analyses isperformed on a Nicolet 380 equipped with the Smart Diffuse Reflectancemodule. All samples are weighed to 3.5±0.5 mg and hand ground with 0.5 gKBr and subsequently pressed and leveled before being inserted into theFT-IR for a 5-minute nitrogen purge. Spectra are recorded in the range400-4000 cm⁻¹.

Scanning Electron Microscopy (“SEM”)

SEM are performed using an Hitachi TM-1000 tungsten filament tabletopmicroscope using a fixed acceleration voltage of 15 kV at a workingpressure of 30-65 Pa, and a single BSE semiconductor detector. Solidsamples are fixed to the stage using a carbon-based adhesive; wetsamples are vacuum dried to a graphite stage prior to analysis. EDSanalysis is performed using an Oxford Instruments SwiftED-TM system, thesensor for which has a detection range of 11Na-92U with an energyresolution of 165 eV.

Chloride: Chloride concentrations are determined with Chloride QuanTab®Test Strips (Product No. 2751340), having a testing range between300-6000 mg chloride per liter solution measured in 100-200 ppmincrements.

X-ray Fluorescence (“XRF”): XRF analyses of solid powder samples areperformed using a Thermo Scientific ARL QUANT′X Energy-Dispersive XRFspectrometer, equipped with a silver anode X-ray source and a Peltiercooled Si(Li) X-ray detector. The samples are pressed into 31 mm pelletsusing an aluminum sample cup. For each sample, three different spectraare gathered, each tailored for analysis of specific elements: the firstusing no X-ray filter at 4 kV, the second using a thin silver filter at18 kV, and the third using a thick silver filter at 30 kV, all undervacuum conditions. Spectra are analyzed using WinTrace software, using aFundamental Parameters analysis method attained from calibration withcertified standard materials.

Thermogravimetric Analysis (“TGA”): TGA analyses of solid powder samplesare performed with a TA Instruments SDT Q600 with simultaneous TGA/DSC(Differential Scanning calorimetry). Samples, in an alumina crucible,are placed into a furnace heated from room temperature to 1000° C. at aconstant ramp rate of 20° C. per minute. The weight loss profile overtemperature is analyzed using Universal Analysis software.

Inductively Coupled Plasma Optical Emission Spectrometry (“ICP-OES”):ICP-OES analyses of typical acidified, liquid samples are performedusing a Thermo ICAP 6500 equipped with a CETAC autosampler. iTEVAcontrol software is used for data acquisition and analysis. Typicaldetection limits for ICP-OES are in the ppm range. Samples that containhigh concentrations of dissolved salts (Na, Ca, Mg) may be analyzedusing the ICAP 6500 equipped with an Elemental Scientific Inc.(ESI)—seaFAST autosampler equipped with a chelation column for matrixelimination analyte pre-concentration.

Example 1 Waste Gas Stream Processing A. Equipment

-   -   System of FIG. 1F        -   Coal-fired boiler (130)        -   Gas-liquid/gas-liquid-solid contactor (112)        -   Recirculation tank (116)        -   Recirculation pump (118)        -   Reactor (114)        -   Base tank (140)

B. Materials

-   -   Coal        -   Bituminous coal (2×500 lbs)        -   Sub-bituminous coal (500 lbs)    -   50% NaOH (90 gallons)    -   CaCl₂ (50 kg)    -   Seawater    -   Freshwater

C. Procedure

The primary feedstocks for the process were 1) coal-derived flue gas toprovide CO₂, SOx, NOx, trace metals, etc., 2) a source of alkalinity toconvert CO₂ to aqueous carbonates and/or bicarbonates, and 3) a sourceof calcium cations to precipitate calcium carbonates.

The CO₂-processing system was operated under conditions simulating atarget commercial process including about 70% CO₂ absorption from fluegas derived from a coal-fired boiler. A two-step process was used withgas-liquid contact and absorption occurring in one unit process toproduce a CO₂-charged solution and precipitation occurring in anotherunit process, wherein the CO₂-charged solution was mixed with a streamof divalent cations to form a slurry comprising carbonate-containingprecipitation material.

The coal-fired boiler simulator (0.3 MW_(th)) provided an approximately50 SCFM slip-stream of flue gas to the CO₂-processing system. The CO₂concentration was controlled to roughly 12-14% by volume. Threedifferent coal types were burned in three successive runs: twobituminous coals from the Raleigh and Dodge Hill mines, and asub-bituminous coal from the Powder River Basin Rawhide mine. The coalsand associated ashes were assayed for trace metals in order to do acomplete accounting of their pathways and fates in the CO₂-processingsystem.

The gas-liquid contactor/absorber was operated under conditions thatmodeled commercial-scale targets of 70% CO₂ absorption and highutilization of alkalinity. The source of alkalinity was about one partin fifty of 50% sodium hydroxide diluted into fresh water.

Precipitation involved mixing a slipstream of CO₂-charged solution withsimulated hard brine as a source of divalent calcium cations. In thiscase, the divalent cation source was calcium chloride dihydratedissolved into fresh water to yield a solution of approximately 0.2 MCa²⁺.

Dewatering was performed using a vacuum filtration method to collectboth the carbonate-containing precipitation material and thesupernatant. The precipitation material was then oven-dried to removedresidual moisture prior to further testing.

Table 2 below shows the various process streams that were sampled, thequantities that were measured, and the testing methods used.

TABLE 2 Process streams sampled, quantities measured, and testingmethods used. Stream measured Measured quantity Testing method Flue gasin/out Trace metals (CAM17) EPA method 29 of absorber HF/HCl EPA method26 SOx EPA method 8 Stable C & O isotopes Liquids in/out of Trace metals(CAM17) EPA methods 200.8/ absorber Stable C & O isotopes 200.7 Solidsin/out Trace metals (CAM17) EPA method 6020 Stable C & O isotopes Mortarpaste leaching Trace metals TCLP

D. Results

Table 3 gives results for HF digestion and subsequent ICP-MS assays ofthe coals used and fly ash samples produced. Molar concentration factorswere calculated using trace metal concentrations and ash percentages foreach coal and ash type. A value of “1” indicates that the same number ofmoles of a metal are in the fly ash as are in the parent coal. A valueof “2” indicates that twice the number of moles of a metal exist in thefly ash relative to the parent coal. A value >1 is contrary toconservation of mass, which may indicate that the ash samples were takenfrom a non-representative portion of the overall particle sizedistribution for all of the ash produced. In addition, the amount ofmetals concentrated in the fly ash might be different depending upon thetemperature history and residence times of the individual ash particles,which is also an unknown. More work may need to be done to fullycharacterize how the trace metals are partitioning into the fly ashstream.

TABLE 3 Results of trace metals assays for coal and fly ash samples. Thefly ash samples were obtained from the baghouse at the end of a 12-hourshift on coal. The concentration factors are in units of moles inash/moles in coal. Duke Energy - Dodge Species (mg Cemex - Raleigh¹Hill¹ PRB - Rawhide² species/kg dry Ash Ash Ash coal/ash “as Conc. Conc.Conc. is”) Coal Ash Factor Coal Ash Factor Coal Ash Factor Ash at 750°C. 12.06 — — 10.09 — — 6.46 — — (%) Cl 0.0337 0.0370 — 0.3151 0.0391 —0.0030 0.0110 — Hg 0.064 0.069 0.13 0.058 0.039 0.067 0.071 0.094 0.086Ag 0.342 4.39 1.55 0.286 4.07 1.44 0.208 3.49 1.08 As 1.92 36.8 2.313.01 58.4 1.96 1.68 43.8 1.68 Ba 118 1060 1.08 41.5 591 1.44 399 66101.07 Be 0.855 10.4 1.47 2.70 31.7 1.18 0.410 8.43 1.33 Cd 0.120 1.431.44 0.451 6.16 1.38 0.080 1.04 0.83 Co 1.99 28.0 1.70 3.00 35.9 1.212.85 51.2 1.16 Cr 35.8 395 1.33 25.0 345 1.39 5.18 124 1.55 Cu 13.4 1371.24 18.9 186 0.99 11.6 187 1.04 Mn 178 1160 0.79 91.1 686 0.76 18.2 2851.01 Mo 1.50 29.2 2.36 6.36 122 1.94 0.615 21.5 2.25 Ni 8.10 103 1.5313.8 169 1.23 7.98 130 1.05 Pb 4.78 72.7 1.83 15.8 213 1.35 2.61 53.01.31 Sb 0.307 4.82 1.89 0.554 8.59 1.56 0.146 4.02 1.78 Se <1 6.85 —1.36 6.27 0.47 <1 16.0 — Tl 0.208 2.30 1.34 0.713 7.85 1.11 0.038 0.9041.54 V 12.6 189 1.81 39.0 516 1.34 17.1 317 1.20 Zn 16.3 167 1.24 37.4516 1.39 28.8 479 1.08 ¹Bituminous coal ²Sub-bituminous coal

Table 4 shows results of flue gas assays using EPA method 29. Combustioncalculations were used to illustrate the concentrations expected if 100%of the trace metals content of the coal went into the flue gas stream.What these data show is that most trace metals (mercury and seleniumexcepted) are refractory enough that only a minor fraction remains inthe flue gas downstream of the baghouse.

TABLE 4 Comparison of theoretical maximum and measured values of fluegas trace metals concentrations. Theoretical values were calculatedusing chemical assays of the raw coal. All ppb values are in terms ofvolume. The theoretical maximum concentrations were determined on acombustion basis of 3.5% excess oxygen. “ND” indicates that the measuredvalue was below the detection limit. The symbol “±” indicates onestandard deviation from the mean value. Cemex - Raleigh¹ Duke Energy -Dodge Hill¹ PRB - Rawhide² Theor. Theor. Theor. 100% Abs. Abs. 100% Abs.Abs. 100% Abs. Abs. in flue inlet outlet in flue inlet outlet in flueinlet outlet gas conc. conc. gas conc. conc. gas conc. conc. Species(ppb) (ppb) (ppb) (ppb) (ppb) (ppb) (ppb) (ppb) (ppb) Hg 0.83 0.25 ±0.05 ND <0.17 0.73 0.18 ± 0.04 ND <0.10 1.05 0.27 ± 0.03 ND <0.21 Ag8.29 0.05 ± 0.01 ND <0.02 6.68 ND <0.02 ND <0.02 5.70 ND <0.02 ND <0.02As 66.98 0.34 ± 0.15 ND <0.03 101.12 0.33 ± 0.07 ND <0.03 66.23 ND <0.03ND <0.03 Ba 2245.87 0.56 ± 0.7  1.35 ± 0.79 760.62 0.44 ± 0.31 0.57 ±0.39 8581.65 1.89 ± 0.52 0.39 ± 0.1  Be 248.03 0.57 ± 0.4  ND <0.09754.27 0.34 ± 0.23 ND <0.09 134.41 0.21 ± 0.04 ND <0.09 Cd 2.79 0.09 ±0.06 0.03 ± 0.01 10.10 ND <0.02 ND <0.02 2.10 0.03 ± 0.01 ND <0.02 Co88.26 ND <0.04 ND <0.04 128.14 ND <0.04 ND <0.04 142.85 ND <0.04 ND<0.04 Cr 1799.62 3.11 ± 1.58 0.75 ± 0.43 1210.20 2.39 ± 1.06 0.81 ± 0.2 294.25 1.18 ± 0.19 0.45 ± 0.07 Cu 551.13 1.32 ± 0.77 0.31 ± 0.14 748.570.87 ± 0.36 0.34 ± 0.09 539.15 0.86 ± 0.13 0.65 ± 0.59 Mo 40.87 0.73 ±0.62 0.59 ± 0.67 166.86 1.00 ± 0.53 0.93 ± 0.48 18.93 1.21 ± 0.62 0.89 ±0.61 Ni 360.61 1.00 ± 0.44 0.50 ± 0.23 591.63 1.38 ± 0.48 1.15 ± 0.78401.47 0.79 ± 0.11 0.57 ± 0.21 Pb 60.30 0.05 ± 0.6  ND <0.01 191.93  ND<0.006  ND <0.006 37.21  ND <0.006  ND <0.006 Sb 6.53 ND <0.03 ND <0.0311.45 ND <0.03 ND <0.03 3.54 ND <0.03 ND <0.03 Se 0 0.56 ± 0.17 ND <0.0543.35 0.96 ± 0.53 ND <0.05 0 ND <0.05 ND <0.05 Tl 2.66 ND <0.02 ND <0.028.78 ND <0.02 ND <0.02 0.55 ND <0.02 ND <0.02 V 646.52 0.54 ± 0.54 ND<0.01 1927.05 0.27 ± 0.3  ND <0.01 991.52 0.15 ± 0.01 ND <0.01 Zn 651.643.07  1.6 ± 1.44 1439.84 4.65 ± 4.33 1.49 ± 0.69 1301.10 2.09 ± 2.030.37 ± 0.44 ¹Bituminous coal ²Sub-bituminous coal

Table 5 shows removal efficiencies calculated from the flue gasconcentrations for each coal type. Removal efficiencies across theabsorber inlet and outlet gas streams were significant for most of themetal species. An interesting feature to note is the dependence ofmercury removal on coal type. Referring to Table 7, the concentration ofchlorine in the coals were ˜0.3 mg/kg for Dodge Hill, ˜0.03 mg/kg forRaleigh, and ˜0.003 mg/kg for Rawhide. The removal efficiency for DodgeHill is roughly twice that of the other, lower chlorine, coals. Thisobservation is likely due to higher levels of water-soluble mercury(II)chloride that would be produced during the combustion of the coal withhigher chloride content.

The overall removal efficiencies in the table show estimates of theproportion of trace metals in the coal feedstock that never make itthrough the absorber and out the stack. This is greater than 99% formost elements, with the exception of mercury, which is of specialimportance because it is the trace element with the most regulatoryinterest. Due to its high volatility, much of the mercury remains in thegas phase and passes through the baghouse. And since a fraction ofelemental mercury is unlikely to be processed, additional controltechnology such as activated carbon injection or supplementalchlorination of the combustion flame to enhance production of oxidizedmercury may be beneficial for complete removal.

TABLE 5 Trace metal removal efficiencies. The first column for each coaltype is the percentage of flue gas trace metals removed from theabsorber flue gas inlet stream. The second column was calculated fromthe initial coal assay and the fraction of trace metals leaving theabsorber in the flue gas. The symbol “—” indicates that the measuredvalues necessary for calculation were below the detection limit. Thesymbol “±” indicates one standard deviation from the mean value. Cemex -Raleigh¹ Duke Energy - Dodge Hill¹ PRB - Rawhide² Abs. Overall Abs.Overall Abs. Overall removal eff. removal eff. removal eff. removal eff.removal eff. removal eff. Species (%) (%) (%) (%) (%) (%) Hg 28 ± 4 79.62 45 ± 26 86.26 22 ± 12 79.91 Ag 54 ± 11 99.76 — 99.70 — 99.65 As90-100 99.96 91-100 99.97 — 99.95 Ba — 99.94 41 ± 16 99.93 72 ± 9 100.00 Be 70-100 99.96 62 ± 27 99.99 44-100 99.93 Cd 47 ± 23 98.92 —99.80 14-100 99.05 Co — 99.95 — 99.97 — 99.97 Cr 69 ± 12 99.96 63 ± 7 99.93 49 ± 13 99.85 Cu 68 ± 11 99.94 57 ± 14 99.95 51 ± 19 99.88 Mo 23 ±45 98.56 3 ± 4 99.44 18 ± 24 95.30 Ni 40 ± 7  99.86 22 ± 24 99.81 11 ±20 99.86 Pb 80.00 99.98 — 100.00 — 99.98 Sb — 99.54 — 99.74 — 99.15 Se89-100 — 92-100 99.88 — — Tl — 99.25 — 99.77 — 96.36 V 93-100 100.0090-100 100.00 88-100 100.00 Zn 38   99.75 51 ± 26 99.90 79-90  99.97¹Bituminous coal ²Sub-bituminous coal

Table 6 gives the absorber inlet/outlet results for various acid gases.Due to the high aqueous solubility and alkaline conditions of thescrubbing technology used in the absorber, very high levels of acid gascapture were achieved. Most notable is the 99.9% removal of SO₂ acrossthe absorber. HF removal was relatively difficult to quantify because ofits concentration relative to detection limits: its removal can only beconstrained across a large range.

TABLE 6 Comparison of acid gas removal efficiencies for the three coaltypes tested. The symbol “±” indicates one standard deviation from themean value. Cemex - Raleigh¹ Duke Energy - Dodge Hill¹ PRB - Rawhide²Abs. Abs. Abs. Abs. Abs. Abs. inlet outlet Removal inlet outlet Removalinlet outlet conc. conc. eff. conc. conc. eff. conc. conc. RemovalSpecies (ppm) (ppm) (%) (ppm) (ppm) (%) (ppm) (ppm) eff. (%) H₂SO₄/ 1.84± 0.36 0.24 ± 0.39 87.6 ± 19.7 2.92 ± 1.8  0.17 ± 0.27  92.4 ± 11.9 2.26± 0.6  0.02 ± 0 99.2 ± 0.2 SO₃ SO₂ 829.7 ± 39.9  0.45 ± 0.15 99.9 ± 0  1872.1 ± 15.2  2.05 ± 3.43 99.9 ± 0.2 263.3 ± 88   0.07 ± 0 99.97 ± 0.01(937.00)³ (1978.00)³ (433.00)³ HCl 5.36 ± 1.94 0.53 ± 0.22 88.5 ± 8.4 27.6 ± 27.1 0.31 ± 0.23 98.7 ± 1.1 3.04 ± 1.02    0.6 ± 0.38 81.4 ± 5.3HF 0.83 ± 0.42 — 28-100 1.00 ± 0.51 — 26-100  0.5 ± 0.18 — 24-100¹Bituminous coal ²Sub-bituminous coal ³Parenthetical value istheoretical maximum concentration of SO₂.

Table 7 gives results for trace metals assays for 1) process water(fresh water), 2) synthetic brine, and 3) supernatant liquid streams.Also given are calculated theoretical maximum levels if 100% of thecoal's metals were to go into the liquid stream, which calculationassumes combustion with 3.5% excess O₂. Ca²⁺ interferes with thereadings of other metals in solution. The result is that the samplesneeded to be significantly diluted to eliminate the Ca²⁺ interference,which, in turn, caused an increase in the detection limit.

TABLE 7 Liquid assay results for the different liquid streams involvedin the absorption and precipitation process. Theoretical values werecalculated using chemical assays of the raw coal assuming combustionwith 3.5% O₂, 100% metal capture, 50 SCFM gas flow, and 10 gpm liquidflow. “ND” indicates that the measured value was below the detectionlimit. The symbol “±” indicates one standard deviation from the meanvalue. Duke Energy - Cemex - Raleigh¹ Dodge Hill¹ PRB - Rawhide² Coal-Coal- Coal- Fresh derived derived derived process Synthetic theor.theor. theor. water brine max Supernatant max Supernatant maxSupernatant Species (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L)(μg/L) Hg ND <0.012 ND <0.24 0.26 ND <0.24 0.22 ND <0.24 0.32 ND <0.24Ag ND <0.19 ND <3.8 1.37 ND <3.8 1.11 ND <3.8 0.94 ND <3.8 As 1.6 ± 0.1ND <10 7.71 ND <10 11.64 ND <10 7.63 ND <10 Ba  45 ± 4.6 ND <100 473.99ND <100 160.53 ND <100 1811.17 ND <100 Be ND <0.5 ND <10 3.43 ND <1010.44 ND <10 1.86 ND <10 Cd ND <0.25 ND <5.0 0.48 ND <5.0 1.74 ND <5.00.36 ND <5.0 Co ND <0.5 12.3 ± 1.4 7.99 ND <10 11.60 ND <10 12.94 ND <10Cr 4.3 ± 0.0 ND <10 143.80 ND <10 96.71 ND <10 23.1 ND <10 Cu 15.3 ±16.9 15-43 53.83 ND <10 73.11 ND <10 52.66 ND <10 Mo ND <0.5 ND <10 6.03ND <10 24.60 ND <10 2.79 ND <10 Ni ND <0.5 ND <10 32.54 ND <10 53.38 ND<10 36.22 ND <10 Pb   3 ± 0.0 ND <10 19.20 ND <10 61.12 ND <10 11.85 ND<10 Sb ND <0.5 ND <10 1.22 ND <10 2.14 ND <10 0.66 ND <10 Se ND <0.5 ND<10 0.00 ND <10 5.26 ND <10 0.00 ND <10 Tl ND <0.5 ND <10 0.84 ND <102.76 ND <10 0.17 ND <10 V 11.5 ± 0.6  ND <10 50.61 ND <10 150.86 ND <1077.62 ND <10 Zn 16.5 ± 5.2  198 ± 27 65.48 ND <100 144.67 ND <100 130.73ND <100 ¹Bituminous coal ²Sub-bituminous coal

Table 8 gives trace metals assays results for the precipitate formed.Detection limits for some metals are comparable to theoretical maximumvalues making quantitation difficult when the sole source of such tracemetals is from coal-derived flue gas; however, trace metals are alsolikely to result from other sources such as the fresh water source, basesource (e.g., natural or industrial waste), and corrosion/leaching fromthe ducts, pipes, and absorber.

TABLE 8 Precipitate assay results for the different coal types.Theoretical values were calculated using chemical assays of the raw coaland assuming combustion with 3.5% O₂, 100% metal capture, and 70% CO₂capture. “ND” indicates that the measured value was below the detectionlimit. The symbol “±” indicates one standard deviation from the meanvalue. Cemex - Raleigh¹ Duke Energy - Dodge Hill¹ PRB - Rawhide² Theor.max Precipitate Theor. max Precipitate Theor. max Precipitate Species(mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) Hg 0.02 ND <0.05 0.01 ND<0.05 0.02 ND <0.05 Ag 0.08 ND <0.5 0.07 ND <0.5 0.05 ND <0.5 As 0.46 ND<0.5 0.71 ND <0.5 0.43 ND <0.5 Ba 28.46 ND <5.0 9.79 6.2 ± 1.4 102.61 ND<5.0 Be 0.21 ND <0.5 0.64 ND <0.5 0.11 ND <0.5 Cd 0.03 ND <0.25 0.11 ND<0.25 0.02 ND <0.25 Co 0.48 0.52 ± 0.01 0.71 0.54 ± 0.02 0.73 0.54 ±0.01 Cr 8.64 0.67 ± 0.18 5.90  1.6 ± 0.28 1.33 ND <0.5 Cu 3.23 1.63 ±0.40 4.46 0.75 ± 0.04 2.98 1.09 ± 0.21 Mo 0.36 ND <0.5 1.50 ND <0.5 0.16ND <0.5 Ni 1.95 0.68 ± 0.27 3.26 ND <0.5 2.05 0.62 ± 0.16 Pb 1.15 ND<0.5 3.73 ND <0.5 0.67 ND <0.5 Sb 0.07 ND <0.5 0.13 ND <0.5 0.04 ND <0.5Se 0.00 ND <0.5 0.32 ND <0.5 0.00 ND <0.5 Tl 0.05 ND <0.5 0.17 ND <0.50.01 ND <0.5 V 3.04 1.13 ± 0.06 9.20 1.13 ± 0.15 4.40 1.2 ± 0.1 Zn 3.9312.67 ± 0.58  8.82 11.33 ± 1.52  7.41 13.3 ± 1.53 ¹Bituminous coal²Sub-bituminous coal

Example 2 Mortar Preparation and Leaching A. Equipment

-   -   Analytical balance (with capability to measure to 0.1 mg)    -   Hobart mixer    -   2″×2″×2″ cube brass mold    -   23° C./98% relative humidity room    -   Compression tester    -   Shatterbox and tungsten carbide grinding container    -   Pipettor (5 mL and 1 mL)    -   pH-meter and calibration solutions for pH-=1.68, 4.0 and 7.0    -   pH paper strips (pH 0-14)    -   1000 mL To-Contain (TC) graduated cylinder    -   2000 mL flask    -   Magnetic stirrer and stir-plate    -   Bottles (Wide-Mouth EP Tox Bottle, Teflon® Resin FEP, NALGENEVWR        #16124-970)    -   Millipore 4-position rotator/agitator    -   Filter holder (polypropylene, 15 cm, VWR #30305-120)    -   Erlenmeyer flask (borosilicate glass, 500 mL, VWR #89000-388)    -   Glass fiber filter paper (Borosilicate 0.7 μm, Whatman GF/F 15        cm Ø, VWR #28497-909)    -   50 mL liquid sample containers for leachate samples

B. Materials

-   -   Portland cement (OPC4-3)    -   Precipitation material (in dry powder form)    -   Reagent grade acetic acid (CH₃COOH, VWR #JT9508-6)    -   Alconox    -   Deionized water    -   18% Nitric acid (for ICP-OES sample acidification)

C. Total Analysis of the Solid Components

The Portland cement lot used for the study as well as the precipitationmaterial was sent out for full digestion and analysis (CAM/CCR 17Metals—Extraction method SW3050B—McCampbell Analytical Lab—1534 WillowPass Rd, Pittsburgh, Calif. 94565).

D. Preparation of Extracting Liquid

Extraction fluid #2 (per §5.7.2 of EPA Test Method 1311) was prepared bydiluting 5.7 mL glacial acetic acid with deionized water to a volume of1 L using a “To Contain” (TC) graduated cylinder. A pH meter wascalibrated using pH 1.68, pH 4.0, and pH 7.0 calibration solutions, andthe pH of extraction fluid was measured at pH 2.88+0.05. Two 1 L batcheswere prepared to match the 80-100 g of ground solid required by themethod. Note that it is necessary to prepare fresh extraction fluid foreach leaching test.

E. Preparation of Paste Samples

Mixing: The paste samples were prepared following the ASTM procedureC305 using a total of 650 g of cementitious materials and a deionizedwater to cementitious material ratio of 0.50. Three 2″×2″×2″ cubes weresubsequently cast in pre-greased brass molds.

Curing: The cube molds were kept in a 98% relative humidity chamber for24 hrs, after which the paste cubes were removed from their molds. Theindividual cubes were then placed on shelves of the 98% relativehumidity room at a 45° angle (such as to not collect water on any one ofthe cube surfaces) for a period of 28 days.

Grinding: At the end of the curing period, each of the three samples waspatted dry and placed in an individual Ziploc® bag. Each cube wasquickly crushed (using a compression tester) inside of its Ziploc® bagbefore grinding in a shatterbox. For each sample, the shatterbox was runfor 10 seconds on about 100 mL of crushed solid to get a fine powderwith some coarse/sand size grains. The particle size distribution ismuch finer than the required particle size distribution by EPA,purposefully chosen in order to test for a worst case scenario.

F. Extraction

The extraction of each sample was carried out following the BottleExtraction method described in §4.2.2 of EPA Test Method 1311. Thebottle was filled with 2 L of extraction liquid #2 to which 100 g ofground solid was added. The lid was tightly closed and taped with ducttape, and the bottle was placed in the rotator-agitator and agitated for18±2 hours. An additional bottle filled with 2 L deionized water wasplaced in one of the holders and agitated for the same amount of time,to provide an aliquot for analysis alongside the other extractedsamples.

G. Filtration

Filtration of each sample was performed using a new borosilicate filterpaper. The pH of filtrate was also measured. A 30 mL aliquot of thefiltrate was subsequently prepared and acidified with 18% nitric acid toa pH of less than or equal to pH 2. A blank filtration sample was alsoprepared using a clean filter and deionized water such that an aliquotcould be submitted for analysis along with the other blank sample andthe leachate.

H. Analysis

The three samples (leachate, bottle blank, and filter blank) wereanalyzed by ICP-OES (Thermo Scientific iCAP 6500 ICP), using QC26 and Hgmethods.

I. Results

Table 9 gives the results of mortar paste leaching studies conductedwith the materials produced. The samples were prepared using a 20%Ordinary Portland Cement (OPC) replacement.

TABLE 9 Precipitate assay results from mortar leaching using the TCLPleaching protocol on 20% OPC replacement mortar paste samples. Thesamples were ground, leached, and the leachate was analyzed at 20-days.The theoretical maximum values for TCLP measurements are based upon thepreviously estimated theoretical maximum values for trace metalsconcentrations in the precipitate with a 100-fold dilution and thecontribution of the 80% of cement. Duke Energy - MCL Cemex - Raleigh¹Dodge Hil¹ PRB - Rawhide² Drinking TCLP Theor. Theor. Theor. Water Reg.TCLP Measured TCLP Measured TCLP Measured Limit Limit Max. TCLP Max.TCLP Max. TCLP Species (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L)(mg/L) Hg 0.002 0.2 0.000 0.000 0.000 0.000 0.000 Ag — 5 0.000 0.0010.000 0.000 0.000 As 0.01 5 0.462 0.005 0.449 0.009 0.457 Ba 2.0 1009.645 1.344 9.679 1.403 9.637 Cd 0.005 1 0.032 0.000 0.032 0.000 0.032Cr 0.1 5 2.092 0.016 2.106 0.025 2.091 Pb 0.015 5 0.228 0.000 0.2280.000 0.228 Se 0.05 1 0.502 0.019 0.352 0.018 0.455 ¹Bituminous coal²Sub-bituminous coal

Example 3 Alternative Mortar Leaching Analysis

In accordance with the procedure outlined in Example 2, mortar cubes areprepared, paste samples of the mortar cubes are prepared, and the pastesamples are extracted with freshly prepared extraction liquid #2. Due topotentially high salt concentrations, filtered extract samples areeither diluted 1:100 prior to analysis by ICP-OES, or filtered extractsamples are processed in an ICP-OES sample introduction system (e.g.,Elemental Scientific Inc. (ESI)—seaFAST) configured with a chelationcolumn for salt matrix elimination and analyte pre-concentration. Inthis example, the ICP-OES sample introduction system is preferred asdilution of the filtered extract samples may result in non-detection ofmany of the analytes of interest.

Example 4 Measurement of δ¹³C Value for Precipitation Material andStarting Materials

This experiment was performed using flue gas resulting from burningpropane and a magnesium-rich industrial waste material. The procedurewas conducted in a container open to the atmosphere.

The starting materials were flue gas from a propane burner, seawater(from around Santa Cruz, Calif.), and brucite (Mg(OH)₂) tailings as themagnesium-rich industrial waste. The brucite tailings were approximately85% Mg(OH)₂, 12% CaCO₃ and 3% SiO₂ as determined by a Rietveld analysisof the X-ray diffraction pattern of a dry aliquot of the tailings.

A container was filled with locally available seawater. Brucite tailingswere added to the seawater, providing an alkaline pH and divalent cationconcentration suitable for precipitation of carbonate-containingprecipitation material without releasing CO₂ into the atmosphere. Fluegas was sparged at a rate and time suitable for precipitation of thecarbonate-containing precipitation material from the alkaline seawatersolution. Sufficient time was allowed for interaction of the componentsof the reaction, after which time the precipitation material wasseparated from the remaining seawater solution, also known as thesupernatant solution, and spray-dried. The resultant powder wassuitable, with further processing, for use as a building material suchas aggregate for use in a roadbed, concrete, or the like. As describedherein, the resultant powder was also suitable for simple storagestored. Alternatively, the precipitation material may have been left inthe seawater solution and stored, optionally after equilibration withatmospheric air.

δ¹³C values for the process starting materials, resultingcarbonate-containing precipitation material and supernatant solutionwere measured. The analysis system used was manufactured by Los GatosResearch and uses direct absorption spectroscopy to provide δ¹³C andconcentration data for gases ranging from 2% to 20% CO₂. The instrumentwas calibrated using standard 5% CO₂ gases with known isotopiccomposition, and measurements of CO₂ evolved from samples of travertineand IAEA marble #20 digested in 2M perchloric acid yielded values thatwere within acceptable measurement error of the values found inliterature. The CO₂ source gas was sampled using a syringe. The CO₂ gaswas passed through a gas dryer (Perma Pure MD Gas Dryer, ModelMD-110-48F-4 made of Nafion® polymer), then into the bench-topcommercially available carbon isotope analysis system. Solid samples,such as the brucite tailings and precipitation material, were firstdigested with heated perchloric acid (2M HClO₄). CO₂ gas was evolvedfrom the closed digestion system, and then passed into the gas dryer.From there, the gas was collected and injected into the analysis system,resulting in δ¹³C data. Similarly, the supernatant solution was digestedto evolve CO₂ gas that was then dried and passed to the analysisinstrument resulting in δ¹³C data.

Measurements from the analysis of the flue gas, industrial waste(brucite tailings), carbonate-containing precipitation material, andsupernatant solution are as follows. The δ¹³C values for theprecipitation material and supernatant solution were −19.92‰ and −24.8‰,respectively. The δ¹³C values of both products of the reaction reflectthe incorporation of the flue gas, CO₂ source, (δ¹³C=−25.00‰) and theinfluence of the brucite tailings that included some calcium carbonate(δ¹³C=−6.73‰). For reference, the δ¹³C value for air is accepted to be−8‰. This example illustrates that δ¹³C values may be used to confirmthe primary source of carbon in a carbonate composition when the CO₂source for the carbonate is combustion, as well as in a solutionproduced from the carbon dioxide.

Example 5 Measurement of δ¹³C Value for Precipitation Material andStarting Materials

This experiment was performed using a bottled mixture of SO₂ and CO₂gases and fly ash as an industrial waste material. The procedure wasconducted in a closed container.

The starting materials were a commercially available bottled mixture ofSO₂ and CO₂ gas, de-ionized water, and fly ash as the industrial wastematerial.

A container was filled with de-ionized water. Fly ash was slaked andadded to the de-ionized water, providing an alkaline pH and divalentcation concentration suitable for precipitation of carbonate-containingprecipitation material without releasing CO₂ into the atmosphere.SO₂/CO₂ gas was sparged at a rate and time suitable for precipitation ofthe carbonate-containing precipitation material from the alkalinesolution. Sufficient time was allowed for interaction of the componentsof the reaction, after which time the precipitation material wasseparated from the remaining solution, also known as the supernatantsolution, and spray-dried. The resultant powder was suitable, withfurther processing, for use, e.g., as a material in the builtenvironment, e.g., as aggregate for use in a road bed, concrete, or thelike. The resultant powder was suitable, with further processing, foruse as a building material such as aggregate for use in a roadbed,concrete, or the like. As described herein, the resultant powder wasalso suitable for simple storage stored. Alternatively, theprecipitation material may have been left in the seawater solution andstored, optionally after equilibration with atmospheric air.

δ¹³ values for the process starting materials, carbonate-containingprecipitation material and supernatant solution were measured asdetailed in Example 4.

Measurements from the analysis of the SO₂/CO₂ gas, industrial waste (flyash), carbonate-containing precipitation material, and supernatantsolution are as follows. The δ¹³C values for the precipitation materialand supernatant solution were −15.88‰ and −11.70‰, respectively. Theδ¹³C values of both products of the reaction reflect the incorporationof the SO₂/CO₂ gas (δ¹³C=−12.45‰) and the fly ash that included somecarbon that was not fully combusted to a gas (δ¹³C=−17.46%). Because thefly ash, itself a product of fossil fuel combustion, had a more negativeδ¹³C than the CO₂ used, the overall δ¹³C value of the precipitationmaterial reflects that by being more negative than that of the CO₂itself. For reference, the δ¹³C value for air is accepted to be −8‰.This example illustrates that δ¹³C values may be used to confirm theprimary source of carbon in a carbonate composition, when a gas mixturethat includes a SOx (SO₂) as well as CO₂ is used.

While preferred embodiments of the invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention. It is intended thatthe following claims define the scope of the invention and that methodsand structures within the scope of these claims and their equivalents becovered thereby.

1-114. (canceled)
 115. A method of treating an industrial waste gas,comprising contacting an industrial waste gas comprising carbon dioxideand at least one other component selected from the group consisting ofNOx, SOx, metal, organic, particulate matter, and a combination thereofwith a waste stream from an industrial process comprising divalentcations and hydroxide ions to form a precipitation material comprisingmetastable carbonate selected from vaterite, aragonite, and acombination thereof and the at least one other component wherein the atleast one other component is precipitated, trapped, adsorbed, or acombination thereof; and combining the precipitation material with waterto convert the metastable carbonate into stable carbonate.
 116. Themethod of claim 1, wherein the waste stream from the industrial processis a liquid, solid, or combination thereof.
 117. The method of claim 1,wherein the waste stream is mining waste, ash, slag, cement kiln waste,oil refinery/petrochemical refinery waste, coal seam waste, paperprocessing waste, water softening waste brine, silicon processing waste,agricultural waste, metal finishing waste, high pH textile waste,caustic sludge, or combinations thereof.
 118. The method of claim 1,wherein the waste stream from the industrial process comprises calciumhydroxide.
 119. The method of claim 1, further comprising adding ammoniato the waste stream.
 120. The method of claim 1, further comprisingadding nitrogenous bases to the waste stream.
 121. The method of claim120, wherein the nitrogenous base is organic amine.
 122. The method ofclaim 1, wherein the at least one other component is sulfate, sulfite,or a combination thereof.
 123. The method of claim 1, wherein theprecipitation material is a slurry comprising solids and supernatant.124. The method of claim 123, further comprising separating the solidsfrom the supernatant.
 125. The method of claim 124, further comprisingrecirculating the supernatant to the waste stream.
 126. The method ofclaim 1, further comprising drying the precipitation material beforecombining with water.
 127. The method of claim 126, wherein theprecipitation material is used to make supplementary cementitiousmaterial, cement, aggregate, mortar, concrete, pozzolan, or acombination thereof.
 128. The method of claim 1, wherein the industrialwaste gas is a gas produced by power plant, chemical processing plant,mechanical processing plant, refinery, cement plant, or steel plant.129. The method of claim 1, wherein the metal is selected from the groupconsisting of antimony, arsenic, barium, beryllium, boron, cadmium,chromium, cobalt, copper, lead, manganese, mercury, molybdenum, nickel,radium, selenium, silver, strontium, thallium, vanadium, and zinc. 130.The method of claim 1, further comprising adding one or more additivesduring the contacting step selected from the group consisting offlocculant, dispersant, surfactant, anti-scalant, crystal growthretarder, and sequestration agent.
 131. The method of claim 1, whereinthe metastable carbonate has a particle size between 0.1 μm to 100 μm.132. The method of claim 1, wherein the metastable carbonate has asurface area between 0.5 to 100 m²/gm.